Endocrinology

Treatment with levothyroxine does not improve the live birth rate in women with thyroid peroxidase antibodies before conception, according to data presented at the annual meeting of the Endocrine Society.

Antonio_Diaz/Thinkstock

Until now, the evidence for the use of levothyroxine in pregnant women with thyroid peroxidase antibodies but normal thyroid function has been inconclusive, Rima K. Dhillon-Smith, MBChB, PhD, of the University of Birmingham (England), and her coauthors said in a paper published simultaneously with the meeting presentation March 23 in the New England Journal of Medicine.

Previous studies have shown that women with thyroid peroxidase antibodies but normal thyroid function have a nearly fourfold higher risk of miscarriage and twofold higher risk of preterm birth, compared with women who don’t have the antibodies.

In the new double-blind study, 952 women with thyroid peroxidase antibodies, normal thyroid function, and a history of miscarriage or infertility were randomized either to daily 50 mcg levothyroxine or placebo, taken from conception to the end of pregnancy.

The rate of pregnancy was similar in the levothyroxine and placebo groups (56.6% vs. 58.3%, respectively), as was the live birth rate (37.4% vs. 37.9%), despite the observation that the levothyroxine group had consistently lower serum thyrotropin and higher free T4 concentrations than did the placebo group.

There were also no significant differences between the two groups in secondary outcomes of miscarriage, preterm birth, or neonatal outcomes such as birth weight.

Researchers also saw no statistically significant differences in the rate of serious adverse events or in the number of women who showed abnormal results on thyroid function tests.

The authors noted that the dosage of levothyroxine used in the study was fixed, leaving the possibility that “the dose may need to be adjusted depending on the participant’s body weight, thyroid peroxidase antibody level, or thyrotropin concentration.”

Existing guidelines from the American Thyroid Association acknowledge the lack of evidence in favor of levothyroxine decreasing the risk of pregnancy loss. However, the guidelines also state that it can be considered in antibody-positive, euthyroid women with a history of loss, “given its potential benefits in comparison with its minimal risk.”

The study was supported by the National Institute for Health Research. No conflicts of interest were declared.

SOURCE: Dhillon-Smith R et al. N Engl J Med. 2019 March 23. doi: 10.1056/NEJMoa1812537

Treatment with levothyroxine does not improve the live birth rate in women with thyroid peroxidase antibodies before conception, according to data presented at the annual meeting of the Endocrine Society.

Antonio_Diaz/Thinkstock

Until now, the evidence for the use of levothyroxine in pregnant women with thyroid peroxidase antibodies but normal thyroid function has been inconclusive, Rima K. Dhillon-Smith, MBChB, PhD, of the University of Birmingham (England), and her coauthors said in a paper published simultaneously with the meeting presentation March 23 in the New England Journal of Medicine.

Previous studies have shown that women with thyroid peroxidase antibodies but normal thyroid function have a nearly fourfold higher risk of miscarriage and twofold higher risk of preterm birth, compared with women who don’t have the antibodies.

In the new double-blind study, 952 women with thyroid peroxidase antibodies, normal thyroid function, and a history of miscarriage or infertility were randomized either to daily 50 mcg levothyroxine or placebo, taken from conception to the end of pregnancy.

The rate of pregnancy was similar in the levothyroxine and placebo groups (56.6% vs. 58.3%, respectively), as was the live birth rate (37.4% vs. 37.9%), despite the observation that the levothyroxine group had consistently lower serum thyrotropin and higher free T4 concentrations than did the placebo group.

There were also no significant differences between the two groups in secondary outcomes of miscarriage, preterm birth, or neonatal outcomes such as birth weight.

Researchers also saw no statistically significant differences in the rate of serious adverse events or in the number of women who showed abnormal results on thyroid function tests.

The authors noted that the dosage of levothyroxine used in the study was fixed, leaving the possibility that “the dose may need to be adjusted depending on the participant’s body weight, thyroid peroxidase antibody level, or thyrotropin concentration.”

Existing guidelines from the American Thyroid Association acknowledge the lack of evidence in favor of levothyroxine decreasing the risk of pregnancy loss. However, the guidelines also state that it can be considered in antibody-positive, euthyroid women with a history of loss, “given its potential benefits in comparison with its minimal risk.”

The study was supported by the National Institute for Health Research. No conflicts of interest were declared.

SOURCE: Dhillon-Smith R et al. N Engl J Med. 2019 March 23. doi: 10.1056/NEJMoa1812537

Treatment with levothyroxine does not improve the live birth rate in women with thyroid peroxidase antibodies before conception, according to data presented at the annual meeting of the Endocrine Society.

Antonio_Diaz/Thinkstock

Until now, the evidence for the use of levothyroxine in pregnant women with thyroid peroxidase antibodies but normal thyroid function has been inconclusive, Rima K. Dhillon-Smith, MBChB, PhD, of the University of Birmingham (England), and her coauthors said in a paper published simultaneously with the meeting presentation March 23 in the New England Journal of Medicine.

Previous studies have shown that women with thyroid peroxidase antibodies but normal thyroid function have a nearly fourfold higher risk of miscarriage and twofold higher risk of preterm birth, compared with women who don’t have the antibodies.

In the new double-blind study, 952 women with thyroid peroxidase antibodies, normal thyroid function, and a history of miscarriage or infertility were randomized either to daily 50 mcg levothyroxine or placebo, taken from conception to the end of pregnancy.

The rate of pregnancy was similar in the levothyroxine and placebo groups (56.6% vs. 58.3%, respectively), as was the live birth rate (37.4% vs. 37.9%), despite the observation that the levothyroxine group had consistently lower serum thyrotropin and higher free T4 concentrations than did the placebo group.

There were also no significant differences between the two groups in secondary outcomes of miscarriage, preterm birth, or neonatal outcomes such as birth weight.

Researchers also saw no statistically significant differences in the rate of serious adverse events or in the number of women who showed abnormal results on thyroid function tests.

The authors noted that the dosage of levothyroxine used in the study was fixed, leaving the possibility that “the dose may need to be adjusted depending on the participant’s body weight, thyroid peroxidase antibody level, or thyrotropin concentration.”

Existing guidelines from the American Thyroid Association acknowledge the lack of evidence in favor of levothyroxine decreasing the risk of pregnancy loss. However, the guidelines also state that it can be considered in antibody-positive, euthyroid women with a history of loss, “given its potential benefits in comparison with its minimal risk.”

The study was supported by the National Institute for Health Research. No conflicts of interest were declared.

SOURCE: Dhillon-Smith R et al. N Engl J Med. 2019 March 23. doi: 10.1056/NEJMoa1812537

The two newer classes of antihyperglycemic drugs that lower cardiovascular risk have different effects on specific cardiovascular and kidney disease outcomes in patients with type 2 diabetes, results of a meta-analysis suggest. Sodium-glucose contransporter-2 (SGLT2) inhibitors significantly reduced hospitalization from heart failure, whereas glucagon-like peptide-1 receptor agonists (GLP-1 RAs) did not, according to the reported results.

The GLP-1–RA class reduced risk of kidney disease progression, largely driven by a reduction in macroalbuminuria, according to the authors, whereas only the SGLT2 inhibitors reduced adverse kidney disease outcomes in a composite excluding that biomarker.

“The prevention of heart failure and progression of kidney disease by SGLT2 [inhibitors] should be considered in the decision-making process when treating patients with type 2 diabetes,” study senior author Marc S. Sabatine, MD, MPH, of Brigham and Women’s Hospital, Boston, and his coauthors wrote in a report on the study appearing in Circulation.

Both GLP-1 RAs and SGLT2 inhibitors significantly reduced major adverse cardiovascular events (MACE) and, as shown in other recent findings, their benefits were confined to patients with established atherosclerotic cardiovascular disease, Dr. Sabatine and his colleagues wrote.

The systematic review and meta-analysis of eight cardiovascular outcomes trials included 77,242 patients, of whom about 56% participated in GLP-1–RA studies and 44% in SGLT2-inhibitor trials. Just under three-quarters of the patients had established atherosclerotic cardiovascular disease, while the remainder had multiple risk factors for it.

Relative risk of hospitalization for heart failure was reduced by 31% with SGLT2 inhibitors, but it was not significantly reduced by GLP-1 RAs, the authors noted.

Risk of kidney disease progression was reduced by 38% with SGLT2 inhibitors and by 18% with GLP-1 RAs when the researchers used a broad composite endpoint including macroalbuminuria, estimated glomerular filtration rate (eGFR), end-stage kidney disease, and death due to renal causes.

By contrast, SGLT2 inhibitors reduced by 45% the relative risk of a narrower kidney outcome that excluded macroalbuminuria, whereas GLP-1 RAs had only a nonsignificant effect on the risk of doubling serum creatinine. That suggests the relative risk reduction of the kidney composite with GLP-1 RAs was driven mainly by a reduction in macroalbuminuria, the authors wrote.

Although albuminuria is an established biomarker for kidney and cardiovascular disease, it is a surrogate marker and can even be absent in patients with reduced eGFR, they said.

“Reduction in eGFR has emerged as a more meaningful endpoint of greater importance and is used in ongoing diabetes trials for kidney outcomes,” the authors said in a discussion of their results.

Relative risk of the composite MACE endpoint, including myocardial infarction, stroke, and cardiovascular death, was reduced by 12% for GLP-1 RAs and by 11% for SGLT2 [inhibitors], according to results of the analysis. However, the benefit was confined to patients with established cardiovascular disease, who had a 14% reduction of risk, compared with no treatment effect in patients who had multiple risk factors only.

Looking at individual MACE components, investigators found that both drug classes significantly reduced relative risk of myocardial infarction and of cardiovascular death, whereas only GLP-1 RAs significantly reduced relative risk of stroke.

Study authors provided disclosures related to AstraZeneca, Amgen, Daiichi-Sankyo, Eisai, GlaxoSmithKline, Intarcia, Janssen Research and Development, and Medimmune, among others.

SOURCE: Zelniker TA et al. Circulation. 2019 Feb 21. doi: 10.1161/CIRCULATIONAHA.118.038868.

The two newer classes of antihyperglycemic drugs that lower cardiovascular risk have different effects on specific cardiovascular and kidney disease outcomes in patients with type 2 diabetes, results of a meta-analysis suggest. Sodium-glucose contransporter-2 (SGLT2) inhibitors significantly reduced hospitalization from heart failure, whereas glucagon-like peptide-1 receptor agonists (GLP-1 RAs) did not, according to the reported results.

The GLP-1–RA class reduced risk of kidney disease progression, largely driven by a reduction in macroalbuminuria, according to the authors, whereas only the SGLT2 inhibitors reduced adverse kidney disease outcomes in a composite excluding that biomarker.

“The prevention of heart failure and progression of kidney disease by SGLT2 [inhibitors] should be considered in the decision-making process when treating patients with type 2 diabetes,” study senior author Marc S. Sabatine, MD, MPH, of Brigham and Women’s Hospital, Boston, and his coauthors wrote in a report on the study appearing in Circulation.

Both GLP-1 RAs and SGLT2 inhibitors significantly reduced major adverse cardiovascular events (MACE) and, as shown in other recent findings, their benefits were confined to patients with established atherosclerotic cardiovascular disease, Dr. Sabatine and his colleagues wrote.

The systematic review and meta-analysis of eight cardiovascular outcomes trials included 77,242 patients, of whom about 56% participated in GLP-1–RA studies and 44% in SGLT2-inhibitor trials. Just under three-quarters of the patients had established atherosclerotic cardiovascular disease, while the remainder had multiple risk factors for it.

Relative risk of hospitalization for heart failure was reduced by 31% with SGLT2 inhibitors, but it was not significantly reduced by GLP-1 RAs, the authors noted.

Risk of kidney disease progression was reduced by 38% with SGLT2 inhibitors and by 18% with GLP-1 RAs when the researchers used a broad composite endpoint including macroalbuminuria, estimated glomerular filtration rate (eGFR), end-stage kidney disease, and death due to renal causes.

By contrast, SGLT2 inhibitors reduced by 45% the relative risk of a narrower kidney outcome that excluded macroalbuminuria, whereas GLP-1 RAs had only a nonsignificant effect on the risk of doubling serum creatinine. That suggests the relative risk reduction of the kidney composite with GLP-1 RAs was driven mainly by a reduction in macroalbuminuria, the authors wrote.

Although albuminuria is an established biomarker for kidney and cardiovascular disease, it is a surrogate marker and can even be absent in patients with reduced eGFR, they said.

“Reduction in eGFR has emerged as a more meaningful endpoint of greater importance and is used in ongoing diabetes trials for kidney outcomes,” the authors said in a discussion of their results.

Relative risk of the composite MACE endpoint, including myocardial infarction, stroke, and cardiovascular death, was reduced by 12% for GLP-1 RAs and by 11% for SGLT2 [inhibitors], according to results of the analysis. However, the benefit was confined to patients with established cardiovascular disease, who had a 14% reduction of risk, compared with no treatment effect in patients who had multiple risk factors only.

Looking at individual MACE components, investigators found that both drug classes significantly reduced relative risk of myocardial infarction and of cardiovascular death, whereas only GLP-1 RAs significantly reduced relative risk of stroke.

Study authors provided disclosures related to AstraZeneca, Amgen, Daiichi-Sankyo, Eisai, GlaxoSmithKline, Intarcia, Janssen Research and Development, and Medimmune, among others.

SOURCE: Zelniker TA et al. Circulation. 2019 Feb 21. doi: 10.1161/CIRCULATIONAHA.118.038868.

The two newer classes of antihyperglycemic drugs that lower cardiovascular risk have different effects on specific cardiovascular and kidney disease outcomes in patients with type 2 diabetes, results of a meta-analysis suggest. Sodium-glucose contransporter-2 (SGLT2) inhibitors significantly reduced hospitalization from heart failure, whereas glucagon-like peptide-1 receptor agonists (GLP-1 RAs) did not, according to the reported results.

The GLP-1–RA class reduced risk of kidney disease progression, largely driven by a reduction in macroalbuminuria, according to the authors, whereas only the SGLT2 inhibitors reduced adverse kidney disease outcomes in a composite excluding that biomarker.

“The prevention of heart failure and progression of kidney disease by SGLT2 [inhibitors] should be considered in the decision-making process when treating patients with type 2 diabetes,” study senior author Marc S. Sabatine, MD, MPH, of Brigham and Women’s Hospital, Boston, and his coauthors wrote in a report on the study appearing in Circulation.

Both GLP-1 RAs and SGLT2 inhibitors significantly reduced major adverse cardiovascular events (MACE) and, as shown in other recent findings, their benefits were confined to patients with established atherosclerotic cardiovascular disease, Dr. Sabatine and his colleagues wrote.

The systematic review and meta-analysis of eight cardiovascular outcomes trials included 77,242 patients, of whom about 56% participated in GLP-1–RA studies and 44% in SGLT2-inhibitor trials. Just under three-quarters of the patients had established atherosclerotic cardiovascular disease, while the remainder had multiple risk factors for it.

Relative risk of hospitalization for heart failure was reduced by 31% with SGLT2 inhibitors, but it was not significantly reduced by GLP-1 RAs, the authors noted.

Risk of kidney disease progression was reduced by 38% with SGLT2 inhibitors and by 18% with GLP-1 RAs when the researchers used a broad composite endpoint including macroalbuminuria, estimated glomerular filtration rate (eGFR), end-stage kidney disease, and death due to renal causes.

By contrast, SGLT2 inhibitors reduced by 45% the relative risk of a narrower kidney outcome that excluded macroalbuminuria, whereas GLP-1 RAs had only a nonsignificant effect on the risk of doubling serum creatinine. That suggests the relative risk reduction of the kidney composite with GLP-1 RAs was driven mainly by a reduction in macroalbuminuria, the authors wrote.

Although albuminuria is an established biomarker for kidney and cardiovascular disease, it is a surrogate marker and can even be absent in patients with reduced eGFR, they said.

“Reduction in eGFR has emerged as a more meaningful endpoint of greater importance and is used in ongoing diabetes trials for kidney outcomes,” the authors said in a discussion of their results.

Relative risk of the composite MACE endpoint, including myocardial infarction, stroke, and cardiovascular death, was reduced by 12% for GLP-1 RAs and by 11% for SGLT2 [inhibitors], according to results of the analysis. However, the benefit was confined to patients with established cardiovascular disease, who had a 14% reduction of risk, compared with no treatment effect in patients who had multiple risk factors only.

Looking at individual MACE components, investigators found that both drug classes significantly reduced relative risk of myocardial infarction and of cardiovascular death, whereas only GLP-1 RAs significantly reduced relative risk of stroke.

Study authors provided disclosures related to AstraZeneca, Amgen, Daiichi-Sankyo, Eisai, GlaxoSmithKline, Intarcia, Janssen Research and Development, and Medimmune, among others.

SOURCE: Zelniker TA et al. Circulation. 2019 Feb 21. doi: 10.1161/CIRCULATIONAHA.118.038868.

NOTE: The scenario presented here is partly based on cases reported elsewhere by Martínez-Valles et al¹ and Fernández-Rodríguez et al.²

A 55-year-old man is admitted to the hospital with generalized malaise, paresthesias, and severe hypertension. He says he had experienced agitation along with weakness on exertion 24 hours before presentation to the emergency department, with subsequent onset of paresthesias in his lower extremities and perioral area.

He is already known to have mild chronic obstructive pulmonary disease, with a ratio of forced expiratory volume in 1 second (FEV₁)to forced vital capacity (FVC) of less than 70% and an FEV₁ 85% of predicted. In addition, he was recently diagnosed with diabetes, resistant hypertension requiring maximum doses of 3 agents (a calcium channel blocker, an angiotensin-converting enzyme inhibitor, and a loop diuretic), and hyperlipidemia.

He is a current smoker with a 30-pack-year smoking history. He does not use alcohol. His family history is noncontributory.

ASSESSING ACID-BASE DISORDERS

1. What type of acid-base disorder does this patient have?

• Metabolic acidosis
• Respiratory acidosis
• Metabolic alkalosis
• Respiratory alkalosis

The patient has metabolic alkalosis.

A 5-step approach

1. Acidosis or alkalosis? The patient’s arterial pH is 7.5, which is alkalemic because it is higher than 7.44.

2. Metabolic or respiratory? The primary process in our patient is overwhelmingly metabolic, as his partial pressure of carbon dioxide (Pco₂) is slightly elevated, a direction that would cause acidosis, not alkalosis.

3. The anion gap (the serum sodium concentration minus the sum of the chloride and bicarbonate concentrations) is normal at 8 mmol/L (DRG:HYBRiD-XL Immunoassay and Clinical Chemistry Analyzer, reference range 8–16).

4. Is the disturbance compensated? We have determined that this patient has a metabolic alkalemia; the question now is whether there is any compensation for the primary disturbance.

In metabolic alkalosis, the Pco₂ may increase by approximately 0.6 mm Hg (range 0.5–0.8) above the nominal normal level of 40 mm Hg for each 1-mmol/L increase in bicarbonate above the nominal normal level of 25 mmol/L.⁴ If the patient requires oxygen, the calculation may be unreliable, however, as hypoxemia may have an overriding influence on respiratory drive.

Patients with chronically high Pco₂ levels such as those with chronic obstructive pulmonary disease can become accustomed to high carbon dioxide levels and lose their hyper-
capnic respiratory drive. Giving oxygen supplementation is thought to decrease respiratory drive in these patients, so that they will breathe slower and retain more carbon dioxide. There is some degree of respiratory compensation for metabolic alkalosis that occurs by breathing less, though it is limited overall—even in very alkalotic patients, breathing less results in CO₂ retention, which, by displacing O₂ molecules in the alveoli, will in turn result in hypoxia. The brain then senses the hypoxia and makes one breathe faster, thereby limiting this compensation. 

This patient’s serum bicarbonate level is 40 mmol/L, or 15 mmol/L higher than the nominal normal level. If he is compensating, his Pco₂ should be 40 + (15 × 0.6) = 49 mm Hg, and in fact it is 51 mm Hg, which is within the normal range of expected compensation (47.5–52 mm Hg). Therefore, yes, he is compensating for the primary disturbance.  

5. In metabolic acidosis, is there a delta gap? As our patient has metabolic alkalosis, not acidosis, this question does not apply in this case.

2. Which is the best test to order next to determine the cause of this patient’s hypokalemic metabolic alkalosis?

• Serum magnesium level
• Spot urine chloride
• Renal ultrasonography
• 24-hour urine collection for sodium, potassium, and chloride

The patient’s loop diuretic is withheld for 12 hours and a spot urine chloride is obtained, which is reported as 44 mmol/L. This high value suggests that a volume-independent hypo­kalemic metabolic alkalosis is present with potassium depletion.

As for the other answer choices:

Serum magnesium. Though hypomagnesemia can cause hypokalemia due to lack of inhibition of renal outer medullary potassium channels and subsequent increased excretion of potassium in the apical tubular membrane, it is not independently associated with acid-base disturbances.⁵

Renal ultrasonography gives information about structural kidney disease but is of limited utility in identifying the cause of hypokalemic metabolic alkalosis.

A 24-hour urine collection is unnecessary in this setting and would ultimately result in delay in diagnosis, as spot urine chloride is a more efficient means of rapidly distinguishing volume-responsive vs volume-independent causes of hypokalemic metabolic alkalosis.⁶

IS HIS HYPERTENSION SECONDARY? IF SO, WHAT IS THE CAUSE?

Several features of this case suggest that the patient’s hypertension is secondary rather than primary. It is of recent onset. The patient’s family history is noncontributory, and his hypertension is resistant to the use of maximum doses of 3 antihypertensive agents.

3. Which of the following causes of secondary hypertension is not commonly associated with hypokalemia and metabolic alkalosis?

• Hyperaldosteronism
• Liddle syndrome
• Cushing syndrome
• Renal parenchymal disease
• Chronic licorice ingestion

Renal parenchymal disease is a cause of resistant hypertension, but it is not characterized by metabolic alkalosis, hypokalemia, and  elevated urine chloride,⁷ while the others listed here—hyperaldosteronism, Liddle syndrome, Cushing syndrome, and chronic licorice ingestion­—are. Other common causes of resistant hypertension without these metabolic abnormalities include obstructive sleep apnea, alcohol abuse, and nonadherence to treatment.

While treatment of hypertension with loop diuretics can result in hypokalemia and metabolic alkalosis due to the effect of these drugs on potassium reabsorption in the loop of Henle, the patient’s hypokalemia persisted after this agent was withdrawn.⁸

Causes of hypokalemic metabolic alkalosis with and without hypertension are further delineated in Figure 1.

Additional diagnostic testing: Plasma renin and plasma aldosterone

At this juncture, the differential diagnosis for this patient’s potassium depletion, metabolic alkalosis, high urine chloride, and hypertension has been narrowed to primary or secondary hyperaldosteronism, surreptitious mineralocorticoid ingestion, Cushing syndrome, licorice ingestion, Liddle syndrome, or one of the 3 hydroxylase deficiencies (11-, 17-, and 21-) (Figure 1).

Although clues in the history, physical examination, and imaging may suggest a specific cause of his abnormal laboratory values, the next step in the diagnostic workup is to measure the plasma renin and aldosterone levels (Table 3).

HYPERALDOSTERONISM

4. Hyperaldosteronism is associated with which of the following patterns of renin and aldosterone values?

• High renin, high aldosterone, normal ratio of plasma aldosterone concentration (PAC) to plasma renin activity (PRA)
• Low renin, low aldosterone, normal PAC–PRA ratio
• Low renin, high aldosterone, high PAC–PRA ratio
• High renin, low aldosterone, low PAC–PRA ratio

The pattern of low renin, high aldosterone, and high PAC–PRA ratio is associated with hyperaldosteronism.

Primary hyperaldosteronism

Primary hyperaldosteronism is one of the most common causes of resistant hypertension and is underappreciated, being diagnosed in up to 20% of patients referred to hypertension specialty clinics.⁷ Potassium levels may be normal, likely contributing to its lack of recognition in this target population.

Primary hyperaldosteronism should be suspected in patients who have a plasma aldosterone PAC–PRA ratio greater than 20 with elevated plasma aldosterone concentrations
(> 15 ng/dL).

Persistently elevated aldosterone levels in the setting of elevated plasma volume is proof that aldosterone secretion is independent of the renin-angiotensin-aldosterone axis, and therefore is autonomous (secondary to adrenal tumor or hyperplasia). Further testing in the form of oral salt loading, saline infusion, or fludrocortisone (a sodium-retaining steroid) administration is thus required to confirm inappropriate, autonomous aldosterone secretion.⁹

After establishing the diagnosis of primary hyperaldosteronism, one should determine the subtype (ie, due to an adrenal carcinoma, unilateral hypersecreting adenoma, or unilateral or bilateral hyperplasia). Further testing includes adrenal computed tomography (CT) to rule out adrenal carcinomas, which are suspected with adenomas larger than 4 cm. Though part of the diagnostic workup, CT as a means of confirmational testing alone does not preclude the possibility of bilateral adrenal hyperplasia in some patients, even in the presence of an adrenal adenoma. For this reason, adrenal venous sampling is required to definitively determine whether the condition is due to a hypersecreting adrenal adenoma or unilateral or bilateral hyperplasia.^9,10

Treatment of primary hyperaldosteronism depends on the subtype of the disease and involves salt restriction in addition to an aldosterone antagonist (spironolactone or eplerenone in the case of bilateral disease) or surgery (unilateral disease).^9,11,12

Secondary hyperaldosteronism

Secondary hyperaldosteronism should be suspected when plasma renin and aldosterone levels are both elevated with a PAC–PRA ratio less than 10.

This pattern is most commonly seen with diuretic use but can also be a consequence of renal artery stenosis or, rarely, a renin-secreting tumor.¹³ Renal artery stenosis is a common finding in patients with hypertension undergoing cardiac catheterization, which is not surprising as more than 90% of such stenoses are atherosclerotic.⁷ Renin-secreting tumors are exceedingly rare, with fewer than 100 cases reported in the literature, and are more common in younger individuals.¹³

Our patient has low-normal aldosterone and plasma renin

On further testing, this patient’s plasma aldosterone level is 2.55 ng/dL (normal < 15 ng/dL), his plasma renin activity is 0.53 ng/mL/hour (normal 0.2–2.8 ng/mL/hour), and his PAC–PRA ratio is therefore 4.81.

The categories discussed thus far have included primary and secondary hyperaldosteronism, which typically do not present with low to normal levels of both renin and aldosterone. Surreptitious mineralocorticoid use could present in this manner, but is unlikely in this patient, whose medications do not include fludrocortisone.

The low-normal values thus lead to consideration of a third category: apparent mineralocorticoid excess. Diseases in this category such as Cushing disease or adrenocorticotropic hormone (ACTH) excess are characterized by increases in corticosteroids so that the potassium depletion, metabolic alkalosis, and hypertension are not a consequence of renin and aldosterone but rather the excess corticosteroids.¹⁴

Causes of apparent mineralocorticoid excess

There are several possible causes of mineralocorticoid excess associated with hypertension and hypokalemic metabolic alkalosis not due to renin and aldosterone.

Chronic licorice ingestion in high volumes is one such cause and is thought to result in inhibition of 11B-hydroxysteroid dehydrogenase or possibly cortisol oxidase by licorice’s active component, glycyrrhetinic acid. This inhibition results in an inability to convert cortisol to cortisone. The cortisol excess binds to mineralocorticoid receptors, and acting like aldosterone, results in hypertension and hypokalemic metabolic alkalosis as well as feedback inhibition of renin and aldosterone levels.¹⁵

Partial hydroxylase deficiencies, though rare, should also be considered as a cause of hypokalemic metabolic alkalosis, hypertension, and, potentially, hirsutism and clitoromegaly in women. They can be diagnosed with elevated levels of 17-ketosteroids and dehydroepiandrosterone sulfate, both of which, in excess, may act on aldosterone receptors in a manner similar to cortisol.¹⁶

Liddle syndrome, a rare autosomal dominant condition, may also present with suppressed levels of both renin and aldosterone. In contrast to the disorders of nonaldosterone mineralocorticoid excess, however, the sodium channel defect in Liddle syndrome is characterized by a primary increase in sodium reabsorption in the collecting tubule and potassium wasting. The resultant volume expansion leads to suppressed renin and aldosterone levels and hypertension with low potassium and elevated bicarbonate concentrations.¹⁷

Liddle syndrome is commonly diagnosed in childhood but may go unrecognized due to occasional absence of hypokalemia at presentation. Potassium-sparing diuretics such as amiloride or triamterene are the mainstays of treatment.¹⁸

Rates of cardiovascular and all-cause mortality are increased in patients with long-term hypercortisolism, even after plasma concentrations of cortisol are normalized.²¹

Figure 2 shows the cascade of the hypothalamic-pituitary-adrenal axis.

Given the patient’s clinical presentation and laboratory and imaging findings with normal plasma renin and aldosterone levels, a workup for suspected hypercortisolism is initiated.

Initial diagnostic testing for hypercortisolism depends on the degree of clinical suspicion. In those with low probability of the disease, testing should consist of 1 of the following, as a single negative test may be sufficient to rule out the disease:

• 24-hour urinary cortisol levels
• Overnight dexamethasone suppression testing
• Late-night salivary cortisol measurements.

In those with a high index of suspicion, 2 of the aforementioned tests should be performed, as 1 normal result may not be sufficient to exclude the diagnosis.^22,23

A 24-hour urinary cortisol collection and overnight dexamethasone suppression test are obtained. His 24-hour urinary free cortisol level is elevated at 6,600 µg (normal 4–100), and suppression testing with 8 mg of dexamethasone (a form of “high-dose” testing)demonstrates only an 8% decline in serum cortisol levels. Cortisol should generally drop more than 90%.

Morning serum cortisol concentration is less than 5 µg/dL (140 nmol/L) in most patients with Cushing disease (ie, a pituitary tumor), and is usually undetectable in normal subjects. Only about 50% of neuroendocrine ACTH-secreting tumors will suppress with this test.

The patient’s clinical presentation, in conjunction with his diagnostic testing, are thus consistent with Cushing syndrome.

CUSHING SYNDROME

Cushing syndrome is most often exogenous or iatrogenic, ie, a result of supraphysiologic doses of glucocorticoids used to treat a variety of inflammatory, autoimmune, and neoplastic conditions.

Endogenous Cushing syndrome, on the other hand, is rare, with an estimated prevalence of 0.7 to 2.4 cases per million per year. ACTH-dependent causes account for 80% of endogenous Cushing syndrome cases, with ACTH-secreting pituitary adenomas (Cushing disease) accounting for 75% to 80% and ectopic ACTH secretion accounting for 15% to 20%. Less than 1% of cases are due to tumors that produce corticotropin-releasing hormone (CRH).

ACTH-independent Cushing syndrome is diagnosed in 20% of endogenous cases and is most commonly caused by a unilateral adrenal tumor. Rare causes of ACTH-independent disease include adrenal carcinoma, McCune-Albright syndrome, and adrenal hyperplasia.²⁴

The patient’s ACTH is high

To determine whether this is an ACTH-dependent or independent process, the next step is to order an ACTH level. His ACTH level is high at 107 pg/mL (normal < 46 pg/mL), confirming the diagnosis of ACTH-dependent Cushing syndrome.

To find out if this ACTH-dependent process is due to a pituitary adenoma, magnetic resonance imaging (MRI) of the pituitary is obtained but is normal.

Large masses (> 6 mm) strongly suggest Cushing disease, but these tumors are often small and may be missed even with more advanced imaging techniques. Corticotropin-secreting adenomas arising from normal cells in the pituitary retain some sensitivity to glucocorticoid negative feedback and CRH stimulation, and thus high-dose dexamethasone suppression testing in conjunction with CRH stimulation testing can be used to differentiate Cushing disease from ectopic ACTH secretion.^24,25 Both of these tests have poor diagnostic accuracy, however, and thus inferior petrosal sampling remains the gold standard for the diagnosis of Cushing disease.

ACTH-SECRETING TUMORS

5. Cushing syndrome due to ectopic ACTH secretion is most commonly attributed to which of the following tumors?

• Small-cell lung carcinoma
• Pancreatic carcinoma
• Medullary thyroid carcinoma
• Gastrinoma

Severe cases of Cushing syndrome are often attributable to ectopic ACTH secretion due to an underlying malignancy, most commonly small-cell lung carcinoma or neuroendocrine tumors of pulmonary origin. Other causes include pancreatic and thymic neuroendocrine tumors, gastrinomas, and medullary thyroid carcinoma.^25,26

Because most ACTH-producing tumors are intrathoracic, initial imaging in cases of suspected ectopic ACTH secretion should focus on the chest, with CT the usual first choice. Octreotide scintigraphy can also be useful in localizing disease, as many neuroendocrine tumors express somatostatin receptors. Specialized positron-emission tomography scans may also be helpful in tumor identification.²⁴

6. Which of the following is most appropriate medical therapy for suppression of cortisol secretion in Cushing syndrome due to ectopic ACTH secretion?

• Spironolactone
• Dexamethasone
• Somatostatin
• Estrogen
• Ketoconazole

Hyperglycemia, hypokalemia, hypertension, psychiatric disturbances, venous thromboembolism, and systemic infections appear to be common in ectopic ACTH syndrome and often correlate with the degree of hypercortisolemia. Severe Cushing syndrome due to ectopic ACTH secretion is an emergency requiring prompt control of cortisol secretion.

First-line treatments include steroidogenesis inhibitors (ketoconazole, metyrapone, etomidate, mitotane) and glucocorticoid receptor antagonists (mifepristone). High-dose spironolactone and eplerenone can also be used to treat the hypertension and hypokalemia associated with mineralocorticoid receptor stimulation. Definitive treatment involves surgical resection, chemotherapy, or radiotherapy when applicable.^24,25

After confirmation of the diagnosis, the patient is prescribed ketoconazole and spironolactone, with substantial improvement. He subsequently is started on combination chemotherapy and radiation therapy for his small-cell lung carcinoma.

DISCUSSION

The differential diagnosis for hypokalemia is broad and relies on information obtained during the history and physical examination, followed by interpretation of selected laboratory results. Myriad pathologies in diverse organ systems, eg, diarrhea, renal tubular acidosis, and adrenal disease, may be responsible for a low serum potassium. Further categorizing potassium depletion on the basis of an associated acid-base disturbance, such as metabolic alkalosis, allows one to use an algorithmic approach that can identify specific etiologies responsible for both the potassium and the acid-base disturbances.

Using the spot urine chloride in the setting of hypokalemic metabolic alkalosis with or without hypertension can narrow the differential diagnosis and allow additional clinical findings to guide clinical problem-solving and decision-making, even for conditions not commonly encountered in routine medical practice.

Obtaining renin and aldosterone measurements in patients with potassium depletion, metabolic alkalosis, high urine chloride excretion, and hypertension permits further categorization into 3 clinical groups: elevated aldosterone and renin (secondary hyperaldosteronism), elevated aldosterone and low renin (primary hyperaldosteronism), or apparent mineralocorticoid excess wherein neither renin nor aldosterone are responsible for the syndrome.

The patient in our case had apparent mineralocorticoid excess as a consequence of an ACTH-producing small-cell carcinoma.

NOTE: The scenario presented here is partly based on cases reported elsewhere by Martínez-Valles et al¹ and Fernández-Rodríguez et al.²

A 55-year-old man is admitted to the hospital with generalized malaise, paresthesias, and severe hypertension. He says he had experienced agitation along with weakness on exertion 24 hours before presentation to the emergency department, with subsequent onset of paresthesias in his lower extremities and perioral area.

He is already known to have mild chronic obstructive pulmonary disease, with a ratio of forced expiratory volume in 1 second (FEV₁)to forced vital capacity (FVC) of less than 70% and an FEV₁ 85% of predicted. In addition, he was recently diagnosed with diabetes, resistant hypertension requiring maximum doses of 3 agents (a calcium channel blocker, an angiotensin-converting enzyme inhibitor, and a loop diuretic), and hyperlipidemia.

He is a current smoker with a 30-pack-year smoking history. He does not use alcohol. His family history is noncontributory.

ASSESSING ACID-BASE DISORDERS

1. What type of acid-base disorder does this patient have?

• Metabolic acidosis
• Respiratory acidosis
• Metabolic alkalosis
• Respiratory alkalosis

The patient has metabolic alkalosis.

A 5-step approach

1. Acidosis or alkalosis? The patient’s arterial pH is 7.5, which is alkalemic because it is higher than 7.44.

2. Metabolic or respiratory? The primary process in our patient is overwhelmingly metabolic, as his partial pressure of carbon dioxide (Pco₂) is slightly elevated, a direction that would cause acidosis, not alkalosis.

3. The anion gap (the serum sodium concentration minus the sum of the chloride and bicarbonate concentrations) is normal at 8 mmol/L (DRG:HYBRiD-XL Immunoassay and Clinical Chemistry Analyzer, reference range 8–16).

4. Is the disturbance compensated? We have determined that this patient has a metabolic alkalemia; the question now is whether there is any compensation for the primary disturbance.

In metabolic alkalosis, the Pco₂ may increase by approximately 0.6 mm Hg (range 0.5–0.8) above the nominal normal level of 40 mm Hg for each 1-mmol/L increase in bicarbonate above the nominal normal level of 25 mmol/L.⁴ If the patient requires oxygen, the calculation may be unreliable, however, as hypoxemia may have an overriding influence on respiratory drive.

Patients with chronically high Pco₂ levels such as those with chronic obstructive pulmonary disease can become accustomed to high carbon dioxide levels and lose their hyper-
capnic respiratory drive. Giving oxygen supplementation is thought to decrease respiratory drive in these patients, so that they will breathe slower and retain more carbon dioxide. There is some degree of respiratory compensation for metabolic alkalosis that occurs by breathing less, though it is limited overall—even in very alkalotic patients, breathing less results in CO₂ retention, which, by displacing O₂ molecules in the alveoli, will in turn result in hypoxia. The brain then senses the hypoxia and makes one breathe faster, thereby limiting this compensation. 

This patient’s serum bicarbonate level is 40 mmol/L, or 15 mmol/L higher than the nominal normal level. If he is compensating, his Pco₂ should be 40 + (15 × 0.6) = 49 mm Hg, and in fact it is 51 mm Hg, which is within the normal range of expected compensation (47.5–52 mm Hg). Therefore, yes, he is compensating for the primary disturbance.  

5. In metabolic acidosis, is there a delta gap? As our patient has metabolic alkalosis, not acidosis, this question does not apply in this case.

2. Which is the best test to order next to determine the cause of this patient’s hypokalemic metabolic alkalosis?

• Serum magnesium level
• Spot urine chloride
• Renal ultrasonography
• 24-hour urine collection for sodium, potassium, and chloride

The patient’s loop diuretic is withheld for 12 hours and a spot urine chloride is obtained, which is reported as 44 mmol/L. This high value suggests that a volume-independent hypo­kalemic metabolic alkalosis is present with potassium depletion.

As for the other answer choices:

Serum magnesium. Though hypomagnesemia can cause hypokalemia due to lack of inhibition of renal outer medullary potassium channels and subsequent increased excretion of potassium in the apical tubular membrane, it is not independently associated with acid-base disturbances.⁵

Renal ultrasonography gives information about structural kidney disease but is of limited utility in identifying the cause of hypokalemic metabolic alkalosis.

A 24-hour urine collection is unnecessary in this setting and would ultimately result in delay in diagnosis, as spot urine chloride is a more efficient means of rapidly distinguishing volume-responsive vs volume-independent causes of hypokalemic metabolic alkalosis.⁶

IS HIS HYPERTENSION SECONDARY? IF SO, WHAT IS THE CAUSE?

Several features of this case suggest that the patient’s hypertension is secondary rather than primary. It is of recent onset. The patient’s family history is noncontributory, and his hypertension is resistant to the use of maximum doses of 3 antihypertensive agents.

3. Which of the following causes of secondary hypertension is not commonly associated with hypokalemia and metabolic alkalosis?

• Hyperaldosteronism
• Liddle syndrome
• Cushing syndrome
• Renal parenchymal disease
• Chronic licorice ingestion

Renal parenchymal disease is a cause of resistant hypertension, but it is not characterized by metabolic alkalosis, hypokalemia, and  elevated urine chloride,⁷ while the others listed here—hyperaldosteronism, Liddle syndrome, Cushing syndrome, and chronic licorice ingestion­—are. Other common causes of resistant hypertension without these metabolic abnormalities include obstructive sleep apnea, alcohol abuse, and nonadherence to treatment.

While treatment of hypertension with loop diuretics can result in hypokalemia and metabolic alkalosis due to the effect of these drugs on potassium reabsorption in the loop of Henle, the patient’s hypokalemia persisted after this agent was withdrawn.⁸

Causes of hypokalemic metabolic alkalosis with and without hypertension are further delineated in Figure 1.

Additional diagnostic testing: Plasma renin and plasma aldosterone

At this juncture, the differential diagnosis for this patient’s potassium depletion, metabolic alkalosis, high urine chloride, and hypertension has been narrowed to primary or secondary hyperaldosteronism, surreptitious mineralocorticoid ingestion, Cushing syndrome, licorice ingestion, Liddle syndrome, or one of the 3 hydroxylase deficiencies (11-, 17-, and 21-) (Figure 1).

Although clues in the history, physical examination, and imaging may suggest a specific cause of his abnormal laboratory values, the next step in the diagnostic workup is to measure the plasma renin and aldosterone levels (Table 3).

HYPERALDOSTERONISM

4. Hyperaldosteronism is associated with which of the following patterns of renin and aldosterone values?

• High renin, high aldosterone, normal ratio of plasma aldosterone concentration (PAC) to plasma renin activity (PRA)
• Low renin, low aldosterone, normal PAC–PRA ratio
• Low renin, high aldosterone, high PAC–PRA ratio
• High renin, low aldosterone, low PAC–PRA ratio

The pattern of low renin, high aldosterone, and high PAC–PRA ratio is associated with hyperaldosteronism.

Primary hyperaldosteronism

Primary hyperaldosteronism is one of the most common causes of resistant hypertension and is underappreciated, being diagnosed in up to 20% of patients referred to hypertension specialty clinics.⁷ Potassium levels may be normal, likely contributing to its lack of recognition in this target population.

Primary hyperaldosteronism should be suspected in patients who have a plasma aldosterone PAC–PRA ratio greater than 20 with elevated plasma aldosterone concentrations
(> 15 ng/dL).

Persistently elevated aldosterone levels in the setting of elevated plasma volume is proof that aldosterone secretion is independent of the renin-angiotensin-aldosterone axis, and therefore is autonomous (secondary to adrenal tumor or hyperplasia). Further testing in the form of oral salt loading, saline infusion, or fludrocortisone (a sodium-retaining steroid) administration is thus required to confirm inappropriate, autonomous aldosterone secretion.⁹

After establishing the diagnosis of primary hyperaldosteronism, one should determine the subtype (ie, due to an adrenal carcinoma, unilateral hypersecreting adenoma, or unilateral or bilateral hyperplasia). Further testing includes adrenal computed tomography (CT) to rule out adrenal carcinomas, which are suspected with adenomas larger than 4 cm. Though part of the diagnostic workup, CT as a means of confirmational testing alone does not preclude the possibility of bilateral adrenal hyperplasia in some patients, even in the presence of an adrenal adenoma. For this reason, adrenal venous sampling is required to definitively determine whether the condition is due to a hypersecreting adrenal adenoma or unilateral or bilateral hyperplasia.^9,10

Treatment of primary hyperaldosteronism depends on the subtype of the disease and involves salt restriction in addition to an aldosterone antagonist (spironolactone or eplerenone in the case of bilateral disease) or surgery (unilateral disease).^9,11,12

Secondary hyperaldosteronism

Secondary hyperaldosteronism should be suspected when plasma renin and aldosterone levels are both elevated with a PAC–PRA ratio less than 10.

This pattern is most commonly seen with diuretic use but can also be a consequence of renal artery stenosis or, rarely, a renin-secreting tumor.¹³ Renal artery stenosis is a common finding in patients with hypertension undergoing cardiac catheterization, which is not surprising as more than 90% of such stenoses are atherosclerotic.⁷ Renin-secreting tumors are exceedingly rare, with fewer than 100 cases reported in the literature, and are more common in younger individuals.¹³

Our patient has low-normal aldosterone and plasma renin

On further testing, this patient’s plasma aldosterone level is 2.55 ng/dL (normal < 15 ng/dL), his plasma renin activity is 0.53 ng/mL/hour (normal 0.2–2.8 ng/mL/hour), and his PAC–PRA ratio is therefore 4.81.

The categories discussed thus far have included primary and secondary hyperaldosteronism, which typically do not present with low to normal levels of both renin and aldosterone. Surreptitious mineralocorticoid use could present in this manner, but is unlikely in this patient, whose medications do not include fludrocortisone.

The low-normal values thus lead to consideration of a third category: apparent mineralocorticoid excess. Diseases in this category such as Cushing disease or adrenocorticotropic hormone (ACTH) excess are characterized by increases in corticosteroids so that the potassium depletion, metabolic alkalosis, and hypertension are not a consequence of renin and aldosterone but rather the excess corticosteroids.¹⁴

Causes of apparent mineralocorticoid excess

There are several possible causes of mineralocorticoid excess associated with hypertension and hypokalemic metabolic alkalosis not due to renin and aldosterone.

Chronic licorice ingestion in high volumes is one such cause and is thought to result in inhibition of 11B-hydroxysteroid dehydrogenase or possibly cortisol oxidase by licorice’s active component, glycyrrhetinic acid. This inhibition results in an inability to convert cortisol to cortisone. The cortisol excess binds to mineralocorticoid receptors, and acting like aldosterone, results in hypertension and hypokalemic metabolic alkalosis as well as feedback inhibition of renin and aldosterone levels.¹⁵

Partial hydroxylase deficiencies, though rare, should also be considered as a cause of hypokalemic metabolic alkalosis, hypertension, and, potentially, hirsutism and clitoromegaly in women. They can be diagnosed with elevated levels of 17-ketosteroids and dehydroepiandrosterone sulfate, both of which, in excess, may act on aldosterone receptors in a manner similar to cortisol.¹⁶

Liddle syndrome, a rare autosomal dominant condition, may also present with suppressed levels of both renin and aldosterone. In contrast to the disorders of nonaldosterone mineralocorticoid excess, however, the sodium channel defect in Liddle syndrome is characterized by a primary increase in sodium reabsorption in the collecting tubule and potassium wasting. The resultant volume expansion leads to suppressed renin and aldosterone levels and hypertension with low potassium and elevated bicarbonate concentrations.¹⁷

Liddle syndrome is commonly diagnosed in childhood but may go unrecognized due to occasional absence of hypokalemia at presentation. Potassium-sparing diuretics such as amiloride or triamterene are the mainstays of treatment.¹⁸

Rates of cardiovascular and all-cause mortality are increased in patients with long-term hypercortisolism, even after plasma concentrations of cortisol are normalized.²¹

Figure 2 shows the cascade of the hypothalamic-pituitary-adrenal axis.

Given the patient’s clinical presentation and laboratory and imaging findings with normal plasma renin and aldosterone levels, a workup for suspected hypercortisolism is initiated.

Initial diagnostic testing for hypercortisolism depends on the degree of clinical suspicion. In those with low probability of the disease, testing should consist of 1 of the following, as a single negative test may be sufficient to rule out the disease:

• 24-hour urinary cortisol levels
• Overnight dexamethasone suppression testing
• Late-night salivary cortisol measurements.

In those with a high index of suspicion, 2 of the aforementioned tests should be performed, as 1 normal result may not be sufficient to exclude the diagnosis.^22,23

A 24-hour urinary cortisol collection and overnight dexamethasone suppression test are obtained. His 24-hour urinary free cortisol level is elevated at 6,600 µg (normal 4–100), and suppression testing with 8 mg of dexamethasone (a form of “high-dose” testing)demonstrates only an 8% decline in serum cortisol levels. Cortisol should generally drop more than 90%.

Morning serum cortisol concentration is less than 5 µg/dL (140 nmol/L) in most patients with Cushing disease (ie, a pituitary tumor), and is usually undetectable in normal subjects. Only about 50% of neuroendocrine ACTH-secreting tumors will suppress with this test.

The patient’s clinical presentation, in conjunction with his diagnostic testing, are thus consistent with Cushing syndrome.

CUSHING SYNDROME

Cushing syndrome is most often exogenous or iatrogenic, ie, a result of supraphysiologic doses of glucocorticoids used to treat a variety of inflammatory, autoimmune, and neoplastic conditions.

Endogenous Cushing syndrome, on the other hand, is rare, with an estimated prevalence of 0.7 to 2.4 cases per million per year. ACTH-dependent causes account for 80% of endogenous Cushing syndrome cases, with ACTH-secreting pituitary adenomas (Cushing disease) accounting for 75% to 80% and ectopic ACTH secretion accounting for 15% to 20%. Less than 1% of cases are due to tumors that produce corticotropin-releasing hormone (CRH).

ACTH-independent Cushing syndrome is diagnosed in 20% of endogenous cases and is most commonly caused by a unilateral adrenal tumor. Rare causes of ACTH-independent disease include adrenal carcinoma, McCune-Albright syndrome, and adrenal hyperplasia.²⁴

The patient’s ACTH is high

To determine whether this is an ACTH-dependent or independent process, the next step is to order an ACTH level. His ACTH level is high at 107 pg/mL (normal < 46 pg/mL), confirming the diagnosis of ACTH-dependent Cushing syndrome.

To find out if this ACTH-dependent process is due to a pituitary adenoma, magnetic resonance imaging (MRI) of the pituitary is obtained but is normal.

Large masses (> 6 mm) strongly suggest Cushing disease, but these tumors are often small and may be missed even with more advanced imaging techniques. Corticotropin-secreting adenomas arising from normal cells in the pituitary retain some sensitivity to glucocorticoid negative feedback and CRH stimulation, and thus high-dose dexamethasone suppression testing in conjunction with CRH stimulation testing can be used to differentiate Cushing disease from ectopic ACTH secretion.^24,25 Both of these tests have poor diagnostic accuracy, however, and thus inferior petrosal sampling remains the gold standard for the diagnosis of Cushing disease.

ACTH-SECRETING TUMORS

5. Cushing syndrome due to ectopic ACTH secretion is most commonly attributed to which of the following tumors?

• Small-cell lung carcinoma
• Pancreatic carcinoma
• Medullary thyroid carcinoma
• Gastrinoma

Severe cases of Cushing syndrome are often attributable to ectopic ACTH secretion due to an underlying malignancy, most commonly small-cell lung carcinoma or neuroendocrine tumors of pulmonary origin. Other causes include pancreatic and thymic neuroendocrine tumors, gastrinomas, and medullary thyroid carcinoma.^25,26

Because most ACTH-producing tumors are intrathoracic, initial imaging in cases of suspected ectopic ACTH secretion should focus on the chest, with CT the usual first choice. Octreotide scintigraphy can also be useful in localizing disease, as many neuroendocrine tumors express somatostatin receptors. Specialized positron-emission tomography scans may also be helpful in tumor identification.²⁴

6. Which of the following is most appropriate medical therapy for suppression of cortisol secretion in Cushing syndrome due to ectopic ACTH secretion?

• Spironolactone
• Dexamethasone
• Somatostatin
• Estrogen
• Ketoconazole

Hyperglycemia, hypokalemia, hypertension, psychiatric disturbances, venous thromboembolism, and systemic infections appear to be common in ectopic ACTH syndrome and often correlate with the degree of hypercortisolemia. Severe Cushing syndrome due to ectopic ACTH secretion is an emergency requiring prompt control of cortisol secretion.

First-line treatments include steroidogenesis inhibitors (ketoconazole, metyrapone, etomidate, mitotane) and glucocorticoid receptor antagonists (mifepristone). High-dose spironolactone and eplerenone can also be used to treat the hypertension and hypokalemia associated with mineralocorticoid receptor stimulation. Definitive treatment involves surgical resection, chemotherapy, or radiotherapy when applicable.^24,25

After confirmation of the diagnosis, the patient is prescribed ketoconazole and spironolactone, with substantial improvement. He subsequently is started on combination chemotherapy and radiation therapy for his small-cell lung carcinoma.

DISCUSSION

The differential diagnosis for hypokalemia is broad and relies on information obtained during the history and physical examination, followed by interpretation of selected laboratory results. Myriad pathologies in diverse organ systems, eg, diarrhea, renal tubular acidosis, and adrenal disease, may be responsible for a low serum potassium. Further categorizing potassium depletion on the basis of an associated acid-base disturbance, such as metabolic alkalosis, allows one to use an algorithmic approach that can identify specific etiologies responsible for both the potassium and the acid-base disturbances.

Using the spot urine chloride in the setting of hypokalemic metabolic alkalosis with or without hypertension can narrow the differential diagnosis and allow additional clinical findings to guide clinical problem-solving and decision-making, even for conditions not commonly encountered in routine medical practice.

Obtaining renin and aldosterone measurements in patients with potassium depletion, metabolic alkalosis, high urine chloride excretion, and hypertension permits further categorization into 3 clinical groups: elevated aldosterone and renin (secondary hyperaldosteronism), elevated aldosterone and low renin (primary hyperaldosteronism), or apparent mineralocorticoid excess wherein neither renin nor aldosterone are responsible for the syndrome.

The patient in our case had apparent mineralocorticoid excess as a consequence of an ACTH-producing small-cell carcinoma.

NOTE: The scenario presented here is partly based on cases reported elsewhere by Martínez-Valles et al¹ and Fernández-Rodríguez et al.²

A 55-year-old man is admitted to the hospital with generalized malaise, paresthesias, and severe hypertension. He says he had experienced agitation along with weakness on exertion 24 hours before presentation to the emergency department, with subsequent onset of paresthesias in his lower extremities and perioral area.

He is already known to have mild chronic obstructive pulmonary disease, with a ratio of forced expiratory volume in 1 second (FEV₁)to forced vital capacity (FVC) of less than 70% and an FEV₁ 85% of predicted. In addition, he was recently diagnosed with diabetes, resistant hypertension requiring maximum doses of 3 agents (a calcium channel blocker, an angiotensin-converting enzyme inhibitor, and a loop diuretic), and hyperlipidemia.

He is a current smoker with a 30-pack-year smoking history. He does not use alcohol. His family history is noncontributory.

ASSESSING ACID-BASE DISORDERS

1. What type of acid-base disorder does this patient have?

• Metabolic acidosis
• Respiratory acidosis
• Metabolic alkalosis
• Respiratory alkalosis

The patient has metabolic alkalosis.

A 5-step approach

1. Acidosis or alkalosis? The patient’s arterial pH is 7.5, which is alkalemic because it is higher than 7.44.

2. Metabolic or respiratory? The primary process in our patient is overwhelmingly metabolic, as his partial pressure of carbon dioxide (Pco₂) is slightly elevated, a direction that would cause acidosis, not alkalosis.

3. The anion gap (the serum sodium concentration minus the sum of the chloride and bicarbonate concentrations) is normal at 8 mmol/L (DRG:HYBRiD-XL Immunoassay and Clinical Chemistry Analyzer, reference range 8–16).

4. Is the disturbance compensated? We have determined that this patient has a metabolic alkalemia; the question now is whether there is any compensation for the primary disturbance.

In metabolic alkalosis, the Pco₂ may increase by approximately 0.6 mm Hg (range 0.5–0.8) above the nominal normal level of 40 mm Hg for each 1-mmol/L increase in bicarbonate above the nominal normal level of 25 mmol/L.⁴ If the patient requires oxygen, the calculation may be unreliable, however, as hypoxemia may have an overriding influence on respiratory drive.

Patients with chronically high Pco₂ levels such as those with chronic obstructive pulmonary disease can become accustomed to high carbon dioxide levels and lose their hyper-
capnic respiratory drive. Giving oxygen supplementation is thought to decrease respiratory drive in these patients, so that they will breathe slower and retain more carbon dioxide. There is some degree of respiratory compensation for metabolic alkalosis that occurs by breathing less, though it is limited overall—even in very alkalotic patients, breathing less results in CO₂ retention, which, by displacing O₂ molecules in the alveoli, will in turn result in hypoxia. The brain then senses the hypoxia and makes one breathe faster, thereby limiting this compensation. 

This patient’s serum bicarbonate level is 40 mmol/L, or 15 mmol/L higher than the nominal normal level. If he is compensating, his Pco₂ should be 40 + (15 × 0.6) = 49 mm Hg, and in fact it is 51 mm Hg, which is within the normal range of expected compensation (47.5–52 mm Hg). Therefore, yes, he is compensating for the primary disturbance.  

5. In metabolic acidosis, is there a delta gap? As our patient has metabolic alkalosis, not acidosis, this question does not apply in this case.

2. Which is the best test to order next to determine the cause of this patient’s hypokalemic metabolic alkalosis?

• Serum magnesium level
• Spot urine chloride
• Renal ultrasonography
• 24-hour urine collection for sodium, potassium, and chloride

The patient’s loop diuretic is withheld for 12 hours and a spot urine chloride is obtained, which is reported as 44 mmol/L. This high value suggests that a volume-independent hypo­kalemic metabolic alkalosis is present with potassium depletion.

As for the other answer choices:

Serum magnesium. Though hypomagnesemia can cause hypokalemia due to lack of inhibition of renal outer medullary potassium channels and subsequent increased excretion of potassium in the apical tubular membrane, it is not independently associated with acid-base disturbances.⁵

Renal ultrasonography gives information about structural kidney disease but is of limited utility in identifying the cause of hypokalemic metabolic alkalosis.

A 24-hour urine collection is unnecessary in this setting and would ultimately result in delay in diagnosis, as spot urine chloride is a more efficient means of rapidly distinguishing volume-responsive vs volume-independent causes of hypokalemic metabolic alkalosis.⁶

IS HIS HYPERTENSION SECONDARY? IF SO, WHAT IS THE CAUSE?

Several features of this case suggest that the patient’s hypertension is secondary rather than primary. It is of recent onset. The patient’s family history is noncontributory, and his hypertension is resistant to the use of maximum doses of 3 antihypertensive agents.

3. Which of the following causes of secondary hypertension is not commonly associated with hypokalemia and metabolic alkalosis?

• Hyperaldosteronism
• Liddle syndrome
• Cushing syndrome
• Renal parenchymal disease
• Chronic licorice ingestion

Renal parenchymal disease is a cause of resistant hypertension, but it is not characterized by metabolic alkalosis, hypokalemia, and  elevated urine chloride,⁷ while the others listed here—hyperaldosteronism, Liddle syndrome, Cushing syndrome, and chronic licorice ingestion­—are. Other common causes of resistant hypertension without these metabolic abnormalities include obstructive sleep apnea, alcohol abuse, and nonadherence to treatment.

While treatment of hypertension with loop diuretics can result in hypokalemia and metabolic alkalosis due to the effect of these drugs on potassium reabsorption in the loop of Henle, the patient’s hypokalemia persisted after this agent was withdrawn.⁸

Causes of hypokalemic metabolic alkalosis with and without hypertension are further delineated in Figure 1.

Additional diagnostic testing: Plasma renin and plasma aldosterone

At this juncture, the differential diagnosis for this patient’s potassium depletion, metabolic alkalosis, high urine chloride, and hypertension has been narrowed to primary or secondary hyperaldosteronism, surreptitious mineralocorticoid ingestion, Cushing syndrome, licorice ingestion, Liddle syndrome, or one of the 3 hydroxylase deficiencies (11-, 17-, and 21-) (Figure 1).

Although clues in the history, physical examination, and imaging may suggest a specific cause of his abnormal laboratory values, the next step in the diagnostic workup is to measure the plasma renin and aldosterone levels (Table 3).

HYPERALDOSTERONISM

4. Hyperaldosteronism is associated with which of the following patterns of renin and aldosterone values?

• High renin, high aldosterone, normal ratio of plasma aldosterone concentration (PAC) to plasma renin activity (PRA)
• Low renin, low aldosterone, normal PAC–PRA ratio
• Low renin, high aldosterone, high PAC–PRA ratio
• High renin, low aldosterone, low PAC–PRA ratio

The pattern of low renin, high aldosterone, and high PAC–PRA ratio is associated with hyperaldosteronism.

Primary hyperaldosteronism

Primary hyperaldosteronism is one of the most common causes of resistant hypertension and is underappreciated, being diagnosed in up to 20% of patients referred to hypertension specialty clinics.⁷ Potassium levels may be normal, likely contributing to its lack of recognition in this target population.

Primary hyperaldosteronism should be suspected in patients who have a plasma aldosterone PAC–PRA ratio greater than 20 with elevated plasma aldosterone concentrations
(> 15 ng/dL).

Persistently elevated aldosterone levels in the setting of elevated plasma volume is proof that aldosterone secretion is independent of the renin-angiotensin-aldosterone axis, and therefore is autonomous (secondary to adrenal tumor or hyperplasia). Further testing in the form of oral salt loading, saline infusion, or fludrocortisone (a sodium-retaining steroid) administration is thus required to confirm inappropriate, autonomous aldosterone secretion.⁹

After establishing the diagnosis of primary hyperaldosteronism, one should determine the subtype (ie, due to an adrenal carcinoma, unilateral hypersecreting adenoma, or unilateral or bilateral hyperplasia). Further testing includes adrenal computed tomography (CT) to rule out adrenal carcinomas, which are suspected with adenomas larger than 4 cm. Though part of the diagnostic workup, CT as a means of confirmational testing alone does not preclude the possibility of bilateral adrenal hyperplasia in some patients, even in the presence of an adrenal adenoma. For this reason, adrenal venous sampling is required to definitively determine whether the condition is due to a hypersecreting adrenal adenoma or unilateral or bilateral hyperplasia.^9,10

Treatment of primary hyperaldosteronism depends on the subtype of the disease and involves salt restriction in addition to an aldosterone antagonist (spironolactone or eplerenone in the case of bilateral disease) or surgery (unilateral disease).^9,11,12

Secondary hyperaldosteronism

Secondary hyperaldosteronism should be suspected when plasma renin and aldosterone levels are both elevated with a PAC–PRA ratio less than 10.

This pattern is most commonly seen with diuretic use but can also be a consequence of renal artery stenosis or, rarely, a renin-secreting tumor.¹³ Renal artery stenosis is a common finding in patients with hypertension undergoing cardiac catheterization, which is not surprising as more than 90% of such stenoses are atherosclerotic.⁷ Renin-secreting tumors are exceedingly rare, with fewer than 100 cases reported in the literature, and are more common in younger individuals.¹³

Our patient has low-normal aldosterone and plasma renin

On further testing, this patient’s plasma aldosterone level is 2.55 ng/dL (normal < 15 ng/dL), his plasma renin activity is 0.53 ng/mL/hour (normal 0.2–2.8 ng/mL/hour), and his PAC–PRA ratio is therefore 4.81.

The categories discussed thus far have included primary and secondary hyperaldosteronism, which typically do not present with low to normal levels of both renin and aldosterone. Surreptitious mineralocorticoid use could present in this manner, but is unlikely in this patient, whose medications do not include fludrocortisone.

The low-normal values thus lead to consideration of a third category: apparent mineralocorticoid excess. Diseases in this category such as Cushing disease or adrenocorticotropic hormone (ACTH) excess are characterized by increases in corticosteroids so that the potassium depletion, metabolic alkalosis, and hypertension are not a consequence of renin and aldosterone but rather the excess corticosteroids.¹⁴

Causes of apparent mineralocorticoid excess

There are several possible causes of mineralocorticoid excess associated with hypertension and hypokalemic metabolic alkalosis not due to renin and aldosterone.

Chronic licorice ingestion in high volumes is one such cause and is thought to result in inhibition of 11B-hydroxysteroid dehydrogenase or possibly cortisol oxidase by licorice’s active component, glycyrrhetinic acid. This inhibition results in an inability to convert cortisol to cortisone. The cortisol excess binds to mineralocorticoid receptors, and acting like aldosterone, results in hypertension and hypokalemic metabolic alkalosis as well as feedback inhibition of renin and aldosterone levels.¹⁵

Partial hydroxylase deficiencies, though rare, should also be considered as a cause of hypokalemic metabolic alkalosis, hypertension, and, potentially, hirsutism and clitoromegaly in women. They can be diagnosed with elevated levels of 17-ketosteroids and dehydroepiandrosterone sulfate, both of which, in excess, may act on aldosterone receptors in a manner similar to cortisol.¹⁶

Liddle syndrome, a rare autosomal dominant condition, may also present with suppressed levels of both renin and aldosterone. In contrast to the disorders of nonaldosterone mineralocorticoid excess, however, the sodium channel defect in Liddle syndrome is characterized by a primary increase in sodium reabsorption in the collecting tubule and potassium wasting. The resultant volume expansion leads to suppressed renin and aldosterone levels and hypertension with low potassium and elevated bicarbonate concentrations.¹⁷

Liddle syndrome is commonly diagnosed in childhood but may go unrecognized due to occasional absence of hypokalemia at presentation. Potassium-sparing diuretics such as amiloride or triamterene are the mainstays of treatment.¹⁸

Rates of cardiovascular and all-cause mortality are increased in patients with long-term hypercortisolism, even after plasma concentrations of cortisol are normalized.²¹

Figure 2 shows the cascade of the hypothalamic-pituitary-adrenal axis.

Given the patient’s clinical presentation and laboratory and imaging findings with normal plasma renin and aldosterone levels, a workup for suspected hypercortisolism is initiated.

Initial diagnostic testing for hypercortisolism depends on the degree of clinical suspicion. In those with low probability of the disease, testing should consist of 1 of the following, as a single negative test may be sufficient to rule out the disease:

• 24-hour urinary cortisol levels
• Overnight dexamethasone suppression testing
• Late-night salivary cortisol measurements.

In those with a high index of suspicion, 2 of the aforementioned tests should be performed, as 1 normal result may not be sufficient to exclude the diagnosis.^22,23

A 24-hour urinary cortisol collection and overnight dexamethasone suppression test are obtained. His 24-hour urinary free cortisol level is elevated at 6,600 µg (normal 4–100), and suppression testing with 8 mg of dexamethasone (a form of “high-dose” testing)demonstrates only an 8% decline in serum cortisol levels. Cortisol should generally drop more than 90%.

Morning serum cortisol concentration is less than 5 µg/dL (140 nmol/L) in most patients with Cushing disease (ie, a pituitary tumor), and is usually undetectable in normal subjects. Only about 50% of neuroendocrine ACTH-secreting tumors will suppress with this test.

The patient’s clinical presentation, in conjunction with his diagnostic testing, are thus consistent with Cushing syndrome.

CUSHING SYNDROME

Cushing syndrome is most often exogenous or iatrogenic, ie, a result of supraphysiologic doses of glucocorticoids used to treat a variety of inflammatory, autoimmune, and neoplastic conditions.

Endogenous Cushing syndrome, on the other hand, is rare, with an estimated prevalence of 0.7 to 2.4 cases per million per year. ACTH-dependent causes account for 80% of endogenous Cushing syndrome cases, with ACTH-secreting pituitary adenomas (Cushing disease) accounting for 75% to 80% and ectopic ACTH secretion accounting for 15% to 20%. Less than 1% of cases are due to tumors that produce corticotropin-releasing hormone (CRH).

ACTH-independent Cushing syndrome is diagnosed in 20% of endogenous cases and is most commonly caused by a unilateral adrenal tumor. Rare causes of ACTH-independent disease include adrenal carcinoma, McCune-Albright syndrome, and adrenal hyperplasia.²⁴

The patient’s ACTH is high

To determine whether this is an ACTH-dependent or independent process, the next step is to order an ACTH level. His ACTH level is high at 107 pg/mL (normal < 46 pg/mL), confirming the diagnosis of ACTH-dependent Cushing syndrome.

To find out if this ACTH-dependent process is due to a pituitary adenoma, magnetic resonance imaging (MRI) of the pituitary is obtained but is normal.

Large masses (> 6 mm) strongly suggest Cushing disease, but these tumors are often small and may be missed even with more advanced imaging techniques. Corticotropin-secreting adenomas arising from normal cells in the pituitary retain some sensitivity to glucocorticoid negative feedback and CRH stimulation, and thus high-dose dexamethasone suppression testing in conjunction with CRH stimulation testing can be used to differentiate Cushing disease from ectopic ACTH secretion.^24,25 Both of these tests have poor diagnostic accuracy, however, and thus inferior petrosal sampling remains the gold standard for the diagnosis of Cushing disease.

ACTH-SECRETING TUMORS

5. Cushing syndrome due to ectopic ACTH secretion is most commonly attributed to which of the following tumors?

• Small-cell lung carcinoma
• Pancreatic carcinoma
• Medullary thyroid carcinoma
• Gastrinoma

Severe cases of Cushing syndrome are often attributable to ectopic ACTH secretion due to an underlying malignancy, most commonly small-cell lung carcinoma or neuroendocrine tumors of pulmonary origin. Other causes include pancreatic and thymic neuroendocrine tumors, gastrinomas, and medullary thyroid carcinoma.^25,26

Because most ACTH-producing tumors are intrathoracic, initial imaging in cases of suspected ectopic ACTH secretion should focus on the chest, with CT the usual first choice. Octreotide scintigraphy can also be useful in localizing disease, as many neuroendocrine tumors express somatostatin receptors. Specialized positron-emission tomography scans may also be helpful in tumor identification.²⁴

6. Which of the following is most appropriate medical therapy for suppression of cortisol secretion in Cushing syndrome due to ectopic ACTH secretion?

• Spironolactone
• Dexamethasone
• Somatostatin
• Estrogen
• Ketoconazole

Hyperglycemia, hypokalemia, hypertension, psychiatric disturbances, venous thromboembolism, and systemic infections appear to be common in ectopic ACTH syndrome and often correlate with the degree of hypercortisolemia. Severe Cushing syndrome due to ectopic ACTH secretion is an emergency requiring prompt control of cortisol secretion.

First-line treatments include steroidogenesis inhibitors (ketoconazole, metyrapone, etomidate, mitotane) and glucocorticoid receptor antagonists (mifepristone). High-dose spironolactone and eplerenone can also be used to treat the hypertension and hypokalemia associated with mineralocorticoid receptor stimulation. Definitive treatment involves surgical resection, chemotherapy, or radiotherapy when applicable.^24,25

After confirmation of the diagnosis, the patient is prescribed ketoconazole and spironolactone, with substantial improvement. He subsequently is started on combination chemotherapy and radiation therapy for his small-cell lung carcinoma.

DISCUSSION

The differential diagnosis for hypokalemia is broad and relies on information obtained during the history and physical examination, followed by interpretation of selected laboratory results. Myriad pathologies in diverse organ systems, eg, diarrhea, renal tubular acidosis, and adrenal disease, may be responsible for a low serum potassium. Further categorizing potassium depletion on the basis of an associated acid-base disturbance, such as metabolic alkalosis, allows one to use an algorithmic approach that can identify specific etiologies responsible for both the potassium and the acid-base disturbances.

Using the spot urine chloride in the setting of hypokalemic metabolic alkalosis with or without hypertension can narrow the differential diagnosis and allow additional clinical findings to guide clinical problem-solving and decision-making, even for conditions not commonly encountered in routine medical practice.

Obtaining renin and aldosterone measurements in patients with potassium depletion, metabolic alkalosis, high urine chloride excretion, and hypertension permits further categorization into 3 clinical groups: elevated aldosterone and renin (secondary hyperaldosteronism), elevated aldosterone and low renin (primary hyperaldosteronism), or apparent mineralocorticoid excess wherein neither renin nor aldosterone are responsible for the syndrome.

The patient in our case had apparent mineralocorticoid excess as a consequence of an ACTH-producing small-cell carcinoma.

The Food and Drug Administration has approved marketing of the Tandem Diabetes Care t:Slim X2 device, the first-ever interoperable, alternate controller–enabled infusion pump, for insulin delivery in children and adults with diabetes.

The pump delivers insulin under the skin at a variable or fixed rate. It can function on its own, or it can be digitally connected to automatically communicate with and receive drug-dosing commands from other diabetes management devices, such as automated insulin-dosing systems, the agency announced.

The approval was based on a review of performance data demonstrating that the device can deliver insulin accurately and reliably and at the rates and volumes programmed by the user. The agency also assessed the pump’s ability to connect reliably with other devices, as well as its cybersecurity and fail-safe modes.

Risks associated with the device were similar to those of other infusion pumps and include infection, bleeding, pain, or skin irritations. Blockages and air bubbles can occur in the tubing, which will affect drug delivery. Risks associated with incorrect drug delivery include hypo- and hyperglycemia as well as diabetic ketoacidosis.

“The marketing authorization of the [pump] has the potential to aid patients who seek more individualized diabetes therapy systems and opens the door for developers of future connected diabetes devices to get other safe and effective products to patients more efficiently,” FDA Commissioner Scott Gottlieb, MD, said in the announcement.

[email protected]

The Food and Drug Administration has approved marketing of the Tandem Diabetes Care t:Slim X2 device, the first-ever interoperable, alternate controller–enabled infusion pump, for insulin delivery in children and adults with diabetes.

The pump delivers insulin under the skin at a variable or fixed rate. It can function on its own, or it can be digitally connected to automatically communicate with and receive drug-dosing commands from other diabetes management devices, such as automated insulin-dosing systems, the agency announced.

The approval was based on a review of performance data demonstrating that the device can deliver insulin accurately and reliably and at the rates and volumes programmed by the user. The agency also assessed the pump’s ability to connect reliably with other devices, as well as its cybersecurity and fail-safe modes.

Risks associated with the device were similar to those of other infusion pumps and include infection, bleeding, pain, or skin irritations. Blockages and air bubbles can occur in the tubing, which will affect drug delivery. Risks associated with incorrect drug delivery include hypo- and hyperglycemia as well as diabetic ketoacidosis.

“The marketing authorization of the [pump] has the potential to aid patients who seek more individualized diabetes therapy systems and opens the door for developers of future connected diabetes devices to get other safe and effective products to patients more efficiently,” FDA Commissioner Scott Gottlieb, MD, said in the announcement.

[email protected]

The Food and Drug Administration has approved marketing of the Tandem Diabetes Care t:Slim X2 device, the first-ever interoperable, alternate controller–enabled infusion pump, for insulin delivery in children and adults with diabetes.

The pump delivers insulin under the skin at a variable or fixed rate. It can function on its own, or it can be digitally connected to automatically communicate with and receive drug-dosing commands from other diabetes management devices, such as automated insulin-dosing systems, the agency announced.

The approval was based on a review of performance data demonstrating that the device can deliver insulin accurately and reliably and at the rates and volumes programmed by the user. The agency also assessed the pump’s ability to connect reliably with other devices, as well as its cybersecurity and fail-safe modes.

Risks associated with the device were similar to those of other infusion pumps and include infection, bleeding, pain, or skin irritations. Blockages and air bubbles can occur in the tubing, which will affect drug delivery. Risks associated with incorrect drug delivery include hypo- and hyperglycemia as well as diabetic ketoacidosis.

“The marketing authorization of the [pump] has the potential to aid patients who seek more individualized diabetes therapy systems and opens the door for developers of future connected diabetes devices to get other safe and effective products to patients more efficiently,” FDA Commissioner Scott Gottlieb, MD, said in the announcement.

[email protected]

Whether subclinical hypothyroidism is clinically important and should be treated remains controversial. Studies have differed in their findings, and although most have found this condition to be associated with a variety of adverse outcomes, large randomized controlled trials are needed to clearly demonstrate its clinical impact in various age groups and the benefit of levothyroxine therapy.

Currently, the best practical approach is to base treatment decisions on the magnitude of elevation of thyroid-stimulating hormone (TSH) and whether the patient has thyroid autoantibodies and associated comorbid conditions.

HIGH TSH, NORMAL FREE T₄ LEVELS

Subclinical hypothyroidism is defined by elevated TSH along with a normal free thyroxine (T₄).¹

The hypothalamic-pituitary-thyroid axis is a balanced homeostatic system, and TSH and thyroid hormone levels have an inverse log-linear relation: if free T₄ and triiodothyronine (T₃) levels go down even a little, TSH levels go up a lot.²

TSH secretion is pulsatile and has a circadian rhythm: serum TSH levels are 50% higher at night and early in the morning than during the rest of the day. Thus, repeated measurements in the same patient can vary by as much as half of the reference range.³

WHAT IS THE UPPER LIMIT OF NORMAL FOR TSH?

The upper limit of normal for TSH, defined as the 97.5th percentile, is approximately 4 or 5 mIU/L depending on the laboratory and the population, but some experts believe it should be lower.³

In favor of a lower upper limit: the distribution of serum TSH levels in the healthy general population does not seem to be a typical bell-shaped Gaussian curve, but rather has a tail at the high end. Some argue that some of the individuals with values in the upper end of the normal range may actually have undiagnosed hypothyroidism and that the upper 97.5th percentile cutoff would be 2.5 mIU/L if these people were excluded.⁴ Also, TSH levels higher than 2.5 mIU/L have been associated with a higher prevalence of antithyroid antibodies and a higher risk of clinical hypothyroidism.⁵

On the other hand, lowering the upper limit of normal to 2.5 mIU/L would result in 4 times as many people receiving a diagnosis of subclinical hypothyroidism, or 22 to 28 million people in the United States.^4,6 Thus, lowering the cutoff may lead to unnecessary therapy and could even harm from overtreatment.

Another argument against lowering the upper limit of normal for TSH is that, with age, serum TSH levels shift higher.⁷ The third National Health and Nutrition Education Survey (NHANES III) found that the 97.5th percentile for serum TSH was 3.56 mIU/L for age group 20 to 29 but 7.49 mIU/L for octogenarians.^7,8

It has been suggested that the upper limit of normal for TSH be adjusted for age, race, sex, and iodine intake.³ Currently available TSH reference ranges are not adjusted for these variables, and there is not enough evidence to suggest age-appropriate ranges,⁹ although higher TSH cutoffs for treatment are advised in elderly patients.¹⁰ Interestingly, higher TSH in older people has been linked to lower mortality rates in some studies.¹¹

Authors of the NHANES III⁸ and Hanford Thyroid Disease study¹² have proposed a cutoff of 4.1 mIU/L for the upper limit of normal for serum TSH in patients with negative antithyroid antibodies and normal findings on thyroid ultrasonography.

SUBCLINICAL HYPOTHYROIDISM IS COMMON

In different studies, the prevalence of subclinical hypothyroidism has been as low as 4% and as high as 20%.^1,8,13 The prevalence is higher in women and increases with age.⁸ It is higher in iodine-sufficient areas, and it increases in iodine-deficient areas with iodine supplementation.¹⁴ Genetics also plays a role, as subclinical hypothyroidism is more common in white people than in African Americans.⁸

A difficulty in estimating the prevalence is the disagreement about the cutoff for TSH, which may differ from that in the general population in certain subgroups such as adolescents, the elderly, and pregnant women.^10,15

A VARIETY OF CAUSES

The most common cause of subclinical hypothyroidism, accounting for 60% to 80% of cases, is Hashimoto (autoimmune) thyroiditis,² in which thyroid peroxidase antibodies are usually present.^2,16

Also important to rule out are false-positive elevations due to substances that interfere with TSH assays (eg, heterophile antibodies, rheumatoid factor, biotin, macro-TSH); reversible causes such as the recovery phase of euthyroid sick syndrome; subacute, painless, or postpartum thyroiditis; central hypo- or hyperthyroidism; and thyroid hormone resistance.

SUBCLINICAL HYPOTHYROIDISM CAN RESOLVE OR PROGRESS 


“Subclinical” suggests that the disease is in its early stage, with changes in TSH already apparent but decreases in thyroid hormone levels yet to come.¹⁷ And indeed, subclinical hypothyroidism can progress to overt hypothyroidism,¹⁸ although it has been reported to resolve spontaneously in half of cases within 2 years,¹⁹ typically in patients with TSH values of 4 to 6 mIU/L.²⁰ The rate of progression to overt hypothyroidism is estimated to be 33% to 55% over 10 to 20 years of follow-up.¹⁸

Figure 1 shows the natural history of subclinical hypothyroidism.¹

GUIDELINES FOR SCREENING DIFFER

Guidelines differ on screening for thyroid disease in the general population, owing to lack of large-scale randomized controlled trials showing treatment benefit in otherwise-healthy people with mildly elevated TSH values.

Various professional societies have adopted different criteria for aggressive case-finding in patients at risk of thyroid disease. Risk factors include family history of thyroid disease, neck irradiation, partial thyroidectomy, dyslipidemia, atrial fibrillation, unexplained weight loss, hyperprolactinemia, autoimmune disorders, and use of medications affecting thyroid function.²³

The US Preventive Services Task Force in 2014 found insufficient evidence on the benefits and harms of screening.²⁴

The American Thyroid Association (ATA) recommends screening adults starting at age 35, with repeat testing every 5 years in patients who have no signs or symptoms of hypothyroidism, and more frequently in those who do.²⁵

The American Association of Clinical Endocrinologists recommends screening in women and older patients. Their guidelines and those of the ATA also suggest screening people at high risk of thyroid disease due to risk factors such as history of autoimmune diseases, neck irradiation, or medications affecting thyroid function.²⁶

The American Academy of Family Physicians recommends screening after age 60.¹⁸

The American College of Physicians recommends screening patients over age 50 who have symptoms.¹⁸

Our approach. Although evidence is lacking to recommend routine screening in adults, aggressive case-finding and treatment in patients at risk of thyroid disease can, we believe, offset the risks associated with subclinical hypothyroidism.²⁴

CLINICAL PRESENTATION

About 70% of patients with subclinical hypothyroidism have no symptoms.¹³

Tiredness was more common in subclinical hypothyroid patients with TSH levels lower than 10 mIU/L compared with euthyroid controls in 1 study, but other studies have been unable to replicate this finding.^27,28

Other frequently reported symptoms include dry skin, cognitive slowing, poor memory, muscle weakness, cold intolerance, constipation, puffy eyes, and hoarseness.¹³

The evidence in favor of levothyroxine therapy to improve symptoms in subclinical hypothyroidism has varied, with some studies showing an improvement in symptom scores compared with placebo, while others have not shown any benefit.^29–31

In one study, the average TSH value for patients whose symptoms did not improve with therapy was 4.6 mIU/L.³¹ An explanation for the lack of effect in this group may be that the TSH values for these patients were in the high-normal range. Also, because most subclinical hypothyroid patients have no symptoms, it is difficult to ascertain symptomatic improvement. Though it is possible to conclude that levothyroxine therapy has a limited role in this group, it is important to also consider the suggestive evidence that untreated subclinical hypothyroidism may lead to increased morbidity and mortality.

ADVERSE EFFECTS OF SUBCLINICAL HYPOTHYROIDISM, EFFECTS OF THERAPY

INDIVIDUALIZED MANAGEMENT AND SHARED DECISION-MAKING

The management of subclinical hypothyroidism should be individualized on the basis of extent of thyroid dysfunction, comorbid conditions, risk factors, and patient preference.¹¹⁸ Shared decision-making is key, weighing the risks and benefits of levothyroxine treatment and the patient’s goals.

The risks of treatment should be kept in mind and explained to the patient. Levothyroxine has a narrow therapeutic range, causing a possibility of overreplacement, and a half-life of 7 days that can cause dosing errors to have longer effect.^118,119

Adherence can be a challenge. The drug needs to be taken on an empty stomach because foods and supplements interfere with its absorption.^118,120 In addition, the cost of medication, frequent biochemical monitoring, and possible need for titration can add to financial burden.

When choosing the dose, one should consider the degree of hypothyroidism or TSH elevation and the patient’s weight, and adjust the dose gently.

If the TSH is high-normal

It is proposed that a TSH range of 3 to 5 mIU/L overlaps with normal thyroid function in a great segment of the population, and at this level it is probably not associated with clinically significant consequences. For these reasons, levothyroxine therapy is not thought to be beneficial for those with TSH in this range.

Pollock et al¹²¹ found that, in patients with symptoms suggesting hypothyroidism and TSH values in the upper end of the normal range, there was no improvement in cognitive function or psychological well-being after 12 weeks of levothyroxine therapy.

However, due to the concern for possible adverse maternal and fetal outcomes and low IQ in children of pregnant patients with subclinical hypothyroidism, levothyroxine therapy is advised in those who are pregnant or planning pregnancy who have TSH levels higher than 2.5 mIU/L, especially if they have thyroid peroxidase antibody. Levothyroxine therapy is not recommended for pregnant patients with negative thyroid peroxidase antibody and TSH within the pregnancy-specific range or less than 4 mIU/L if the reference ranges are unavailable.

Keep in mind that, even at these TSH values, there is risk of progression to overt hypothyroidism, especially in the presence of thyroid peroxidase antibody, so patients in this group should be monitored closely.

If TSH is mildly elevated

The evidence to support levothyroxine therapy in patients with subclinical hypothyroidism with TSH levels less than 10 mIU/L remains inconclusive, and the decision to treat should be based on clinical judgment.² The studies that have looked at the benefit of treating subclinical hypothyroidism in terms of cardiac, neuromuscular, cognitive, and neuropsychiatric outcomes have included patients with a wide range of TSH levels, and some of these studies were not stratified on the basis of degree of TSH elevation.

The risk that subclinical hypothyroidism will progress to overt hypothyroidism in patients with TSH higher than 8 mIU/L is high, and in 70% of these patients, the TSH level rises to more than 10 mIU/L within 4 years. Early treatment should be considered if the TSH is higher than 7 or 8 mIU/L.

If TSH is higher than 10 mIU/L

Figure 2 outlines an algorithmic approach to subclinical hypothyroidism in nonpregnant patients as suggested by Peeters.¹²²

Whether subclinical hypothyroidism is clinically important and should be treated remains controversial. Studies have differed in their findings, and although most have found this condition to be associated with a variety of adverse outcomes, large randomized controlled trials are needed to clearly demonstrate its clinical impact in various age groups and the benefit of levothyroxine therapy.

Currently, the best practical approach is to base treatment decisions on the magnitude of elevation of thyroid-stimulating hormone (TSH) and whether the patient has thyroid autoantibodies and associated comorbid conditions.

HIGH TSH, NORMAL FREE T₄ LEVELS

Subclinical hypothyroidism is defined by elevated TSH along with a normal free thyroxine (T₄).¹

The hypothalamic-pituitary-thyroid axis is a balanced homeostatic system, and TSH and thyroid hormone levels have an inverse log-linear relation: if free T₄ and triiodothyronine (T₃) levels go down even a little, TSH levels go up a lot.²

TSH secretion is pulsatile and has a circadian rhythm: serum TSH levels are 50% higher at night and early in the morning than during the rest of the day. Thus, repeated measurements in the same patient can vary by as much as half of the reference range.³

WHAT IS THE UPPER LIMIT OF NORMAL FOR TSH?

The upper limit of normal for TSH, defined as the 97.5th percentile, is approximately 4 or 5 mIU/L depending on the laboratory and the population, but some experts believe it should be lower.³

In favor of a lower upper limit: the distribution of serum TSH levels in the healthy general population does not seem to be a typical bell-shaped Gaussian curve, but rather has a tail at the high end. Some argue that some of the individuals with values in the upper end of the normal range may actually have undiagnosed hypothyroidism and that the upper 97.5th percentile cutoff would be 2.5 mIU/L if these people were excluded.⁴ Also, TSH levels higher than 2.5 mIU/L have been associated with a higher prevalence of antithyroid antibodies and a higher risk of clinical hypothyroidism.⁵

On the other hand, lowering the upper limit of normal to 2.5 mIU/L would result in 4 times as many people receiving a diagnosis of subclinical hypothyroidism, or 22 to 28 million people in the United States.^4,6 Thus, lowering the cutoff may lead to unnecessary therapy and could even harm from overtreatment.

Another argument against lowering the upper limit of normal for TSH is that, with age, serum TSH levels shift higher.⁷ The third National Health and Nutrition Education Survey (NHANES III) found that the 97.5th percentile for serum TSH was 3.56 mIU/L for age group 20 to 29 but 7.49 mIU/L for octogenarians.^7,8

It has been suggested that the upper limit of normal for TSH be adjusted for age, race, sex, and iodine intake.³ Currently available TSH reference ranges are not adjusted for these variables, and there is not enough evidence to suggest age-appropriate ranges,⁹ although higher TSH cutoffs for treatment are advised in elderly patients.¹⁰ Interestingly, higher TSH in older people has been linked to lower mortality rates in some studies.¹¹

Authors of the NHANES III⁸ and Hanford Thyroid Disease study¹² have proposed a cutoff of 4.1 mIU/L for the upper limit of normal for serum TSH in patients with negative antithyroid antibodies and normal findings on thyroid ultrasonography.

SUBCLINICAL HYPOTHYROIDISM IS COMMON

In different studies, the prevalence of subclinical hypothyroidism has been as low as 4% and as high as 20%.^1,8,13 The prevalence is higher in women and increases with age.⁸ It is higher in iodine-sufficient areas, and it increases in iodine-deficient areas with iodine supplementation.¹⁴ Genetics also plays a role, as subclinical hypothyroidism is more common in white people than in African Americans.⁸

A difficulty in estimating the prevalence is the disagreement about the cutoff for TSH, which may differ from that in the general population in certain subgroups such as adolescents, the elderly, and pregnant women.^10,15

A VARIETY OF CAUSES

The most common cause of subclinical hypothyroidism, accounting for 60% to 80% of cases, is Hashimoto (autoimmune) thyroiditis,² in which thyroid peroxidase antibodies are usually present.^2,16

Also important to rule out are false-positive elevations due to substances that interfere with TSH assays (eg, heterophile antibodies, rheumatoid factor, biotin, macro-TSH); reversible causes such as the recovery phase of euthyroid sick syndrome; subacute, painless, or postpartum thyroiditis; central hypo- or hyperthyroidism; and thyroid hormone resistance.

SUBCLINICAL HYPOTHYROIDISM CAN RESOLVE OR PROGRESS 


“Subclinical” suggests that the disease is in its early stage, with changes in TSH already apparent but decreases in thyroid hormone levels yet to come.¹⁷ And indeed, subclinical hypothyroidism can progress to overt hypothyroidism,¹⁸ although it has been reported to resolve spontaneously in half of cases within 2 years,¹⁹ typically in patients with TSH values of 4 to 6 mIU/L.²⁰ The rate of progression to overt hypothyroidism is estimated to be 33% to 55% over 10 to 20 years of follow-up.¹⁸

Figure 1 shows the natural history of subclinical hypothyroidism.¹

GUIDELINES FOR SCREENING DIFFER

Guidelines differ on screening for thyroid disease in the general population, owing to lack of large-scale randomized controlled trials showing treatment benefit in otherwise-healthy people with mildly elevated TSH values.

Various professional societies have adopted different criteria for aggressive case-finding in patients at risk of thyroid disease. Risk factors include family history of thyroid disease, neck irradiation, partial thyroidectomy, dyslipidemia, atrial fibrillation, unexplained weight loss, hyperprolactinemia, autoimmune disorders, and use of medications affecting thyroid function.²³

The US Preventive Services Task Force in 2014 found insufficient evidence on the benefits and harms of screening.²⁴

The American Thyroid Association (ATA) recommends screening adults starting at age 35, with repeat testing every 5 years in patients who have no signs or symptoms of hypothyroidism, and more frequently in those who do.²⁵

The American Association of Clinical Endocrinologists recommends screening in women and older patients. Their guidelines and those of the ATA also suggest screening people at high risk of thyroid disease due to risk factors such as history of autoimmune diseases, neck irradiation, or medications affecting thyroid function.²⁶

The American Academy of Family Physicians recommends screening after age 60.¹⁸

The American College of Physicians recommends screening patients over age 50 who have symptoms.¹⁸

Our approach. Although evidence is lacking to recommend routine screening in adults, aggressive case-finding and treatment in patients at risk of thyroid disease can, we believe, offset the risks associated with subclinical hypothyroidism.²⁴

CLINICAL PRESENTATION

About 70% of patients with subclinical hypothyroidism have no symptoms.¹³

Tiredness was more common in subclinical hypothyroid patients with TSH levels lower than 10 mIU/L compared with euthyroid controls in 1 study, but other studies have been unable to replicate this finding.^27,28

Other frequently reported symptoms include dry skin, cognitive slowing, poor memory, muscle weakness, cold intolerance, constipation, puffy eyes, and hoarseness.¹³

The evidence in favor of levothyroxine therapy to improve symptoms in subclinical hypothyroidism has varied, with some studies showing an improvement in symptom scores compared with placebo, while others have not shown any benefit.^29–31

In one study, the average TSH value for patients whose symptoms did not improve with therapy was 4.6 mIU/L.³¹ An explanation for the lack of effect in this group may be that the TSH values for these patients were in the high-normal range. Also, because most subclinical hypothyroid patients have no symptoms, it is difficult to ascertain symptomatic improvement. Though it is possible to conclude that levothyroxine therapy has a limited role in this group, it is important to also consider the suggestive evidence that untreated subclinical hypothyroidism may lead to increased morbidity and mortality.

ADVERSE EFFECTS OF SUBCLINICAL HYPOTHYROIDISM, EFFECTS OF THERAPY

INDIVIDUALIZED MANAGEMENT AND SHARED DECISION-MAKING

The management of subclinical hypothyroidism should be individualized on the basis of extent of thyroid dysfunction, comorbid conditions, risk factors, and patient preference.¹¹⁸ Shared decision-making is key, weighing the risks and benefits of levothyroxine treatment and the patient’s goals.

The risks of treatment should be kept in mind and explained to the patient. Levothyroxine has a narrow therapeutic range, causing a possibility of overreplacement, and a half-life of 7 days that can cause dosing errors to have longer effect.^118,119

Adherence can be a challenge. The drug needs to be taken on an empty stomach because foods and supplements interfere with its absorption.^118,120 In addition, the cost of medication, frequent biochemical monitoring, and possible need for titration can add to financial burden.

When choosing the dose, one should consider the degree of hypothyroidism or TSH elevation and the patient’s weight, and adjust the dose gently.

If the TSH is high-normal

It is proposed that a TSH range of 3 to 5 mIU/L overlaps with normal thyroid function in a great segment of the population, and at this level it is probably not associated with clinically significant consequences. For these reasons, levothyroxine therapy is not thought to be beneficial for those with TSH in this range.

Pollock et al¹²¹ found that, in patients with symptoms suggesting hypothyroidism and TSH values in the upper end of the normal range, there was no improvement in cognitive function or psychological well-being after 12 weeks of levothyroxine therapy.

However, due to the concern for possible adverse maternal and fetal outcomes and low IQ in children of pregnant patients with subclinical hypothyroidism, levothyroxine therapy is advised in those who are pregnant or planning pregnancy who have TSH levels higher than 2.5 mIU/L, especially if they have thyroid peroxidase antibody. Levothyroxine therapy is not recommended for pregnant patients with negative thyroid peroxidase antibody and TSH within the pregnancy-specific range or less than 4 mIU/L if the reference ranges are unavailable.

Keep in mind that, even at these TSH values, there is risk of progression to overt hypothyroidism, especially in the presence of thyroid peroxidase antibody, so patients in this group should be monitored closely.

If TSH is mildly elevated

The evidence to support levothyroxine therapy in patients with subclinical hypothyroidism with TSH levels less than 10 mIU/L remains inconclusive, and the decision to treat should be based on clinical judgment.² The studies that have looked at the benefit of treating subclinical hypothyroidism in terms of cardiac, neuromuscular, cognitive, and neuropsychiatric outcomes have included patients with a wide range of TSH levels, and some of these studies were not stratified on the basis of degree of TSH elevation.

The risk that subclinical hypothyroidism will progress to overt hypothyroidism in patients with TSH higher than 8 mIU/L is high, and in 70% of these patients, the TSH level rises to more than 10 mIU/L within 4 years. Early treatment should be considered if the TSH is higher than 7 or 8 mIU/L.

If TSH is higher than 10 mIU/L

Figure 2 outlines an algorithmic approach to subclinical hypothyroidism in nonpregnant patients as suggested by Peeters.¹²²

Whether subclinical hypothyroidism is clinically important and should be treated remains controversial. Studies have differed in their findings, and although most have found this condition to be associated with a variety of adverse outcomes, large randomized controlled trials are needed to clearly demonstrate its clinical impact in various age groups and the benefit of levothyroxine therapy.

Currently, the best practical approach is to base treatment decisions on the magnitude of elevation of thyroid-stimulating hormone (TSH) and whether the patient has thyroid autoantibodies and associated comorbid conditions.

HIGH TSH, NORMAL FREE T₄ LEVELS

Subclinical hypothyroidism is defined by elevated TSH along with a normal free thyroxine (T₄).¹

The hypothalamic-pituitary-thyroid axis is a balanced homeostatic system, and TSH and thyroid hormone levels have an inverse log-linear relation: if free T₄ and triiodothyronine (T₃) levels go down even a little, TSH levels go up a lot.²

TSH secretion is pulsatile and has a circadian rhythm: serum TSH levels are 50% higher at night and early in the morning than during the rest of the day. Thus, repeated measurements in the same patient can vary by as much as half of the reference range.³

WHAT IS THE UPPER LIMIT OF NORMAL FOR TSH?

The upper limit of normal for TSH, defined as the 97.5th percentile, is approximately 4 or 5 mIU/L depending on the laboratory and the population, but some experts believe it should be lower.³

In favor of a lower upper limit: the distribution of serum TSH levels in the healthy general population does not seem to be a typical bell-shaped Gaussian curve, but rather has a tail at the high end. Some argue that some of the individuals with values in the upper end of the normal range may actually have undiagnosed hypothyroidism and that the upper 97.5th percentile cutoff would be 2.5 mIU/L if these people were excluded.⁴ Also, TSH levels higher than 2.5 mIU/L have been associated with a higher prevalence of antithyroid antibodies and a higher risk of clinical hypothyroidism.⁵

On the other hand, lowering the upper limit of normal to 2.5 mIU/L would result in 4 times as many people receiving a diagnosis of subclinical hypothyroidism, or 22 to 28 million people in the United States.^4,6 Thus, lowering the cutoff may lead to unnecessary therapy and could even harm from overtreatment.

Another argument against lowering the upper limit of normal for TSH is that, with age, serum TSH levels shift higher.⁷ The third National Health and Nutrition Education Survey (NHANES III) found that the 97.5th percentile for serum TSH was 3.56 mIU/L for age group 20 to 29 but 7.49 mIU/L for octogenarians.^7,8

It has been suggested that the upper limit of normal for TSH be adjusted for age, race, sex, and iodine intake.³ Currently available TSH reference ranges are not adjusted for these variables, and there is not enough evidence to suggest age-appropriate ranges,⁹ although higher TSH cutoffs for treatment are advised in elderly patients.¹⁰ Interestingly, higher TSH in older people has been linked to lower mortality rates in some studies.¹¹

Authors of the NHANES III⁸ and Hanford Thyroid Disease study¹² have proposed a cutoff of 4.1 mIU/L for the upper limit of normal for serum TSH in patients with negative antithyroid antibodies and normal findings on thyroid ultrasonography.

SUBCLINICAL HYPOTHYROIDISM IS COMMON

In different studies, the prevalence of subclinical hypothyroidism has been as low as 4% and as high as 20%.^1,8,13 The prevalence is higher in women and increases with age.⁸ It is higher in iodine-sufficient areas, and it increases in iodine-deficient areas with iodine supplementation.¹⁴ Genetics also plays a role, as subclinical hypothyroidism is more common in white people than in African Americans.⁸

A difficulty in estimating the prevalence is the disagreement about the cutoff for TSH, which may differ from that in the general population in certain subgroups such as adolescents, the elderly, and pregnant women.^10,15

A VARIETY OF CAUSES

The most common cause of subclinical hypothyroidism, accounting for 60% to 80% of cases, is Hashimoto (autoimmune) thyroiditis,² in which thyroid peroxidase antibodies are usually present.^2,16

Also important to rule out are false-positive elevations due to substances that interfere with TSH assays (eg, heterophile antibodies, rheumatoid factor, biotin, macro-TSH); reversible causes such as the recovery phase of euthyroid sick syndrome; subacute, painless, or postpartum thyroiditis; central hypo- or hyperthyroidism; and thyroid hormone resistance.

SUBCLINICAL HYPOTHYROIDISM CAN RESOLVE OR PROGRESS 


“Subclinical” suggests that the disease is in its early stage, with changes in TSH already apparent but decreases in thyroid hormone levels yet to come.¹⁷ And indeed, subclinical hypothyroidism can progress to overt hypothyroidism,¹⁸ although it has been reported to resolve spontaneously in half of cases within 2 years,¹⁹ typically in patients with TSH values of 4 to 6 mIU/L.²⁰ The rate of progression to overt hypothyroidism is estimated to be 33% to 55% over 10 to 20 years of follow-up.¹⁸

Figure 1 shows the natural history of subclinical hypothyroidism.¹

GUIDELINES FOR SCREENING DIFFER

Guidelines differ on screening for thyroid disease in the general population, owing to lack of large-scale randomized controlled trials showing treatment benefit in otherwise-healthy people with mildly elevated TSH values.

Various professional societies have adopted different criteria for aggressive case-finding in patients at risk of thyroid disease. Risk factors include family history of thyroid disease, neck irradiation, partial thyroidectomy, dyslipidemia, atrial fibrillation, unexplained weight loss, hyperprolactinemia, autoimmune disorders, and use of medications affecting thyroid function.²³

The US Preventive Services Task Force in 2014 found insufficient evidence on the benefits and harms of screening.²⁴

The American Thyroid Association (ATA) recommends screening adults starting at age 35, with repeat testing every 5 years in patients who have no signs or symptoms of hypothyroidism, and more frequently in those who do.²⁵

The American Association of Clinical Endocrinologists recommends screening in women and older patients. Their guidelines and those of the ATA also suggest screening people at high risk of thyroid disease due to risk factors such as history of autoimmune diseases, neck irradiation, or medications affecting thyroid function.²⁶

The American Academy of Family Physicians recommends screening after age 60.¹⁸

The American College of Physicians recommends screening patients over age 50 who have symptoms.¹⁸

Our approach. Although evidence is lacking to recommend routine screening in adults, aggressive case-finding and treatment in patients at risk of thyroid disease can, we believe, offset the risks associated with subclinical hypothyroidism.²⁴

CLINICAL PRESENTATION

About 70% of patients with subclinical hypothyroidism have no symptoms.¹³

Tiredness was more common in subclinical hypothyroid patients with TSH levels lower than 10 mIU/L compared with euthyroid controls in 1 study, but other studies have been unable to replicate this finding.^27,28

Other frequently reported symptoms include dry skin, cognitive slowing, poor memory, muscle weakness, cold intolerance, constipation, puffy eyes, and hoarseness.¹³

The evidence in favor of levothyroxine therapy to improve symptoms in subclinical hypothyroidism has varied, with some studies showing an improvement in symptom scores compared with placebo, while others have not shown any benefit.^29–31

In one study, the average TSH value for patients whose symptoms did not improve with therapy was 4.6 mIU/L.³¹ An explanation for the lack of effect in this group may be that the TSH values for these patients were in the high-normal range. Also, because most subclinical hypothyroid patients have no symptoms, it is difficult to ascertain symptomatic improvement. Though it is possible to conclude that levothyroxine therapy has a limited role in this group, it is important to also consider the suggestive evidence that untreated subclinical hypothyroidism may lead to increased morbidity and mortality.

ADVERSE EFFECTS OF SUBCLINICAL HYPOTHYROIDISM, EFFECTS OF THERAPY

INDIVIDUALIZED MANAGEMENT AND SHARED DECISION-MAKING

The management of subclinical hypothyroidism should be individualized on the basis of extent of thyroid dysfunction, comorbid conditions, risk factors, and patient preference.¹¹⁸ Shared decision-making is key, weighing the risks and benefits of levothyroxine treatment and the patient’s goals.

The risks of treatment should be kept in mind and explained to the patient. Levothyroxine has a narrow therapeutic range, causing a possibility of overreplacement, and a half-life of 7 days that can cause dosing errors to have longer effect.^118,119

Adherence can be a challenge. The drug needs to be taken on an empty stomach because foods and supplements interfere with its absorption.^118,120 In addition, the cost of medication, frequent biochemical monitoring, and possible need for titration can add to financial burden.

When choosing the dose, one should consider the degree of hypothyroidism or TSH elevation and the patient’s weight, and adjust the dose gently.

If the TSH is high-normal

It is proposed that a TSH range of 3 to 5 mIU/L overlaps with normal thyroid function in a great segment of the population, and at this level it is probably not associated with clinically significant consequences. For these reasons, levothyroxine therapy is not thought to be beneficial for those with TSH in this range.

Pollock et al¹²¹ found that, in patients with symptoms suggesting hypothyroidism and TSH values in the upper end of the normal range, there was no improvement in cognitive function or psychological well-being after 12 weeks of levothyroxine therapy.

However, due to the concern for possible adverse maternal and fetal outcomes and low IQ in children of pregnant patients with subclinical hypothyroidism, levothyroxine therapy is advised in those who are pregnant or planning pregnancy who have TSH levels higher than 2.5 mIU/L, especially if they have thyroid peroxidase antibody. Levothyroxine therapy is not recommended for pregnant patients with negative thyroid peroxidase antibody and TSH within the pregnancy-specific range or less than 4 mIU/L if the reference ranges are unavailable.

Keep in mind that, even at these TSH values, there is risk of progression to overt hypothyroidism, especially in the presence of thyroid peroxidase antibody, so patients in this group should be monitored closely.

If TSH is mildly elevated

The evidence to support levothyroxine therapy in patients with subclinical hypothyroidism with TSH levels less than 10 mIU/L remains inconclusive, and the decision to treat should be based on clinical judgment.² The studies that have looked at the benefit of treating subclinical hypothyroidism in terms of cardiac, neuromuscular, cognitive, and neuropsychiatric outcomes have included patients with a wide range of TSH levels, and some of these studies were not stratified on the basis of degree of TSH elevation.

The risk that subclinical hypothyroidism will progress to overt hypothyroidism in patients with TSH higher than 8 mIU/L is high, and in 70% of these patients, the TSH level rises to more than 10 mIU/L within 4 years. Early treatment should be considered if the TSH is higher than 7 or 8 mIU/L.

If TSH is higher than 10 mIU/L

Figure 2 outlines an algorithmic approach to subclinical hypothyroidism in nonpregnant patients as suggested by Peeters.¹²²

At a quick read, the messages from these articles may seem contradictory. But the biology is more complex in the setting of endogenous production of T₄ by the thyroid gland, which is regulated by TSH, which in turn is regulated in a feedback loop by the thyroid-produced T₄. In the setting of a fixed replacement dose of exogenous levothyroxine, the provided hormone affects the pituitary production of TSH, which likely will have no significant subsequent effect on the T₄ level. Thus, the feedback control loop is far simpler.

There has not been a definitive study demonstrating that thyroxine supplementation in patients with subclinical hypothyroidism results in a superior clinical outcome. There are hints that this may be the case, and Azim and Nasr cite some of these studies. Recognizing a few markedly different physiologic reasons why the TSH can be slightly elevated and the T₄ normal helps explain the lack of uniform clinical success with supplementation therapy and provides rationales for some management strategies.

Any biological variability in the responsiveness of the thyroid gland to TSH may affect the relationship between the levels of TSH and thyroid gland-released T₄. In theory, if the thyroid receptor has decreased affinity for TSH, a higher TSH concentration will be needed to get the thyroid gland to secrete the level of T₄ that the pituitary sensing mechanism deems normal for that individual. If the receptor affinity was decreased due to a gene polymorphism, this relationship between TSH and T₄ may be stable, and providing exogenous T₄ will result in a lower, “normalized” TSH level but may disrupt the thyroid-pituitary crosstalk and may even produce clinical hyperthyroidism.

A similar scenario exists in the setting of early thyroid gland failure, such as in Hashimoto thyroiditis. But in the latter scenario, the TSH-to-T₄ production relationship may be unstable over time, for as additional thyroid gland is destroyed, T₄ production will continue to decrease, the TSH will increase, and the thyroid gland may ultimately fail and hypothyroidism will occur. Hence the recommendation that in the setting of subclinical hypothyroidism and antiperoxidase antibodies, T₄ and TSH levels should be monitored regularly in order to detect early true thyroid gland failure when the T₄ level can no longer be maintained despite the increased stimulation of the gland by the elevated TSH. Analogous to this may be subclinical hypothyroidism in the elderly, in whom thyroid gland failure may develop, despite an increased TSH, from senescence rather than autoimmunity. What I am suggesting is that the natural history of all patients with subclinical hypothyroidism is not alike, and it thus should not be surprising that there does not seem to be a one-size-fits-all approach to management.

Symptoms in patients with subclinical hypothyroidism have not uniformly improved with T₄ treatment compared with placebo. Notably, most patients with subclinical hypothyroidism experience no symptoms. But consider the extremely common symptom of fatigue, which can be present for a myriad of defined and undefined reasons. This symptom may often lead physicians to check the TSH and, if that is even slightly elevated, to also check the T₄. It may also lead some physicians to routinely check the T₄. Subclinical hypothyroidism is also quite common; thus, by chance alone or because of the circadian timing of checking the TSH, a slightly elevated TSH and fatigue may coexist and yet be unrelated.

Additionally, a positive biochemical response to thyroxine supplementation, such as a lowering of cholesterol, does not prove that the patient was clinically hypothyroid prior to supplementation, any more than lowering a patient’s blood glucose with insulin proves that the patient was diabetic. The management of subclinical hypothyroidism should be nuanced and based on both clinical and laboratory parameters.

At a quick read, the messages from these articles may seem contradictory. But the biology is more complex in the setting of endogenous production of T₄ by the thyroid gland, which is regulated by TSH, which in turn is regulated in a feedback loop by the thyroid-produced T₄. In the setting of a fixed replacement dose of exogenous levothyroxine, the provided hormone affects the pituitary production of TSH, which likely will have no significant subsequent effect on the T₄ level. Thus, the feedback control loop is far simpler.

There has not been a definitive study demonstrating that thyroxine supplementation in patients with subclinical hypothyroidism results in a superior clinical outcome. There are hints that this may be the case, and Azim and Nasr cite some of these studies. Recognizing a few markedly different physiologic reasons why the TSH can be slightly elevated and the T₄ normal helps explain the lack of uniform clinical success with supplementation therapy and provides rationales for some management strategies.

Any biological variability in the responsiveness of the thyroid gland to TSH may affect the relationship between the levels of TSH and thyroid gland-released T₄. In theory, if the thyroid receptor has decreased affinity for TSH, a higher TSH concentration will be needed to get the thyroid gland to secrete the level of T₄ that the pituitary sensing mechanism deems normal for that individual. If the receptor affinity was decreased due to a gene polymorphism, this relationship between TSH and T₄ may be stable, and providing exogenous T₄ will result in a lower, “normalized” TSH level but may disrupt the thyroid-pituitary crosstalk and may even produce clinical hyperthyroidism.

A similar scenario exists in the setting of early thyroid gland failure, such as in Hashimoto thyroiditis. But in the latter scenario, the TSH-to-T₄ production relationship may be unstable over time, for as additional thyroid gland is destroyed, T₄ production will continue to decrease, the TSH will increase, and the thyroid gland may ultimately fail and hypothyroidism will occur. Hence the recommendation that in the setting of subclinical hypothyroidism and antiperoxidase antibodies, T₄ and TSH levels should be monitored regularly in order to detect early true thyroid gland failure when the T₄ level can no longer be maintained despite the increased stimulation of the gland by the elevated TSH. Analogous to this may be subclinical hypothyroidism in the elderly, in whom thyroid gland failure may develop, despite an increased TSH, from senescence rather than autoimmunity. What I am suggesting is that the natural history of all patients with subclinical hypothyroidism is not alike, and it thus should not be surprising that there does not seem to be a one-size-fits-all approach to management.

Symptoms in patients with subclinical hypothyroidism have not uniformly improved with T₄ treatment compared with placebo. Notably, most patients with subclinical hypothyroidism experience no symptoms. But consider the extremely common symptom of fatigue, which can be present for a myriad of defined and undefined reasons. This symptom may often lead physicians to check the TSH and, if that is even slightly elevated, to also check the T₄. It may also lead some physicians to routinely check the T₄. Subclinical hypothyroidism is also quite common; thus, by chance alone or because of the circadian timing of checking the TSH, a slightly elevated TSH and fatigue may coexist and yet be unrelated.

Additionally, a positive biochemical response to thyroxine supplementation, such as a lowering of cholesterol, does not prove that the patient was clinically hypothyroid prior to supplementation, any more than lowering a patient’s blood glucose with insulin proves that the patient was diabetic. The management of subclinical hypothyroidism should be nuanced and based on both clinical and laboratory parameters.

At a quick read, the messages from these articles may seem contradictory. But the biology is more complex in the setting of endogenous production of T₄ by the thyroid gland, which is regulated by TSH, which in turn is regulated in a feedback loop by the thyroid-produced T₄. In the setting of a fixed replacement dose of exogenous levothyroxine, the provided hormone affects the pituitary production of TSH, which likely will have no significant subsequent effect on the T₄ level. Thus, the feedback control loop is far simpler.

There has not been a definitive study demonstrating that thyroxine supplementation in patients with subclinical hypothyroidism results in a superior clinical outcome. There are hints that this may be the case, and Azim and Nasr cite some of these studies. Recognizing a few markedly different physiologic reasons why the TSH can be slightly elevated and the T₄ normal helps explain the lack of uniform clinical success with supplementation therapy and provides rationales for some management strategies.

Any biological variability in the responsiveness of the thyroid gland to TSH may affect the relationship between the levels of TSH and thyroid gland-released T₄. In theory, if the thyroid receptor has decreased affinity for TSH, a higher TSH concentration will be needed to get the thyroid gland to secrete the level of T₄ that the pituitary sensing mechanism deems normal for that individual. If the receptor affinity was decreased due to a gene polymorphism, this relationship between TSH and T₄ may be stable, and providing exogenous T₄ will result in a lower, “normalized” TSH level but may disrupt the thyroid-pituitary crosstalk and may even produce clinical hyperthyroidism.

A similar scenario exists in the setting of early thyroid gland failure, such as in Hashimoto thyroiditis. But in the latter scenario, the TSH-to-T₄ production relationship may be unstable over time, for as additional thyroid gland is destroyed, T₄ production will continue to decrease, the TSH will increase, and the thyroid gland may ultimately fail and hypothyroidism will occur. Hence the recommendation that in the setting of subclinical hypothyroidism and antiperoxidase antibodies, T₄ and TSH levels should be monitored regularly in order to detect early true thyroid gland failure when the T₄ level can no longer be maintained despite the increased stimulation of the gland by the elevated TSH. Analogous to this may be subclinical hypothyroidism in the elderly, in whom thyroid gland failure may develop, despite an increased TSH, from senescence rather than autoimmunity. What I am suggesting is that the natural history of all patients with subclinical hypothyroidism is not alike, and it thus should not be surprising that there does not seem to be a one-size-fits-all approach to management.

Symptoms in patients with subclinical hypothyroidism have not uniformly improved with T₄ treatment compared with placebo. Notably, most patients with subclinical hypothyroidism experience no symptoms. But consider the extremely common symptom of fatigue, which can be present for a myriad of defined and undefined reasons. This symptom may often lead physicians to check the TSH and, if that is even slightly elevated, to also check the T₄. It may also lead some physicians to routinely check the T₄. Subclinical hypothyroidism is also quite common; thus, by chance alone or because of the circadian timing of checking the TSH, a slightly elevated TSH and fatigue may coexist and yet be unrelated.

Additionally, a positive biochemical response to thyroxine supplementation, such as a lowering of cholesterol, does not prove that the patient was clinically hypothyroid prior to supplementation, any more than lowering a patient’s blood glucose with insulin proves that the patient was diabetic. The management of subclinical hypothyroidism should be nuanced and based on both clinical and laboratory parameters.

CHICAGO – The short-term risk of developing heart failure in patients with newly identified hypothyroidism, be it overt or subclinical, is double that of euthyroid individuals, Caroline H. Noergaard, MD, reported at the American Heart Association scientific sessions.

Bruce Jancin/MDedge News

“This is really important clinically. The association with heart failure has previously been shown in both overt and subclinical hyperthyroidism, but it’s actually new knowledge that hypothyroidism is associated with immediate risk of heart failure. And a lot of people have subclinical hypothyroidism,” said Dr. Noergaard, a PhD student in epidemiology at Aalborg (Denmark) University.

Also at the meeting, Jeffrey L. Anderson, MD, reported that free thyroxine levels within the normal reference range were associated in graded fashion with an increased prevalence and incidence of atrial fibrillation in a large Utah study, a finding that provides independent confirmation of an earlier report by investigators from the population-based Rotterdam Study.

“These findings validate those of the Rotterdam Study in a much larger dataset and may have important clinical implications, including a redefinition of the reference range and the target-free T₄ levels for thyroxine replacement therapy,” observed Dr. Anderson, professor of internal medicine at the University of Utah, Salt Lake City, and a research cardiologist at the Intermountain Medical Center Heart Institute.

Hypothyroidism and heart failure

Dr. Noergaard presented a retrospective study of over 1 million Copenhagen-area adults (mean age, 50 years) with no history of heart failure, who had their first thyroid function test. She and her coinvestigators turned to comprehensive Danish national health care registries to determine how many of these individuals were diagnosed with new-onset heart failure within 90 days after their thyroid function test.

Subclinical hypothyroidism was defined by a thyroid-stimulating hormone level greater than 5 mIU/L and a free T₄ of 9-22 pmol/L. Overt hypothyroidism required a TSH greater than 5 mIU/L with a free T₄ less than 9 pmol/L.

Free T₄ predicts atrial fibrillation risk

Dr. Anderson presented a retrospective analysis of 174,914 adult patients in the Intermountain Healthcare EMR database, none of whom were on thyroid replacement at entry. The patients, who were a mean age of 64 years and 65% women, were followed for an average of 6.3 years. Of these, 88.4% had a free T₄ within the normal reference range of 0.75-1.5 ng/dL, 7.4% had a value below the cutoff for normal, and 4.2% had a free T₄ above the reference range.

Upon dividing the patients within the normal range into quartiles based upon their free T₄ level, he and his coinvestigators found that the baseline prevalence of atrial fibrillation was 8.7% in those in quartile 1, 9.3% in quartile 2, 10.5% in quartile 3, and 12.6% in quartile 4. In a multivariate analysis adjusted for potential confounders, the risk of prevalent atrial fibrillation was increased by 11% for patients in quartile 2, compared with those in the first quartile, by 22% in quartile 3, and by 40% in quartile 4.

The incidence of new-onset atrial fibrillation during 3 years of follow-up was 4.1% in patients in normal-range quartile 1, 4.3% in quartile 2, 4.5% in quartile 3, and 5.2% in the top normal-range quartile. The odds of developing atrial fibrillation were increased by 8% and 16% in quartiles 3 and 4, compared with quartile 1.

Serum TSH and free T₃ levels showed no consistent relationship with atrial fibrillation.

The Utah findings confirm in a large U.S. population the earlier report from the Rotterdam Study (J Clin Endocrinol Metab. 2015 Oct;100(10):3718-24).

Dr. Noergaard and Dr. Anderson reported having no financial conflicts regarding their studies, which were carried out free of commercial support.

[email protected]

CHICAGO – The short-term risk of developing heart failure in patients with newly identified hypothyroidism, be it overt or subclinical, is double that of euthyroid individuals, Caroline H. Noergaard, MD, reported at the American Heart Association scientific sessions.

Bruce Jancin/MDedge News

“This is really important clinically. The association with heart failure has previously been shown in both overt and subclinical hyperthyroidism, but it’s actually new knowledge that hypothyroidism is associated with immediate risk of heart failure. And a lot of people have subclinical hypothyroidism,” said Dr. Noergaard, a PhD student in epidemiology at Aalborg (Denmark) University.

Also at the meeting, Jeffrey L. Anderson, MD, reported that free thyroxine levels within the normal reference range were associated in graded fashion with an increased prevalence and incidence of atrial fibrillation in a large Utah study, a finding that provides independent confirmation of an earlier report by investigators from the population-based Rotterdam Study.

“These findings validate those of the Rotterdam Study in a much larger dataset and may have important clinical implications, including a redefinition of the reference range and the target-free T₄ levels for thyroxine replacement therapy,” observed Dr. Anderson, professor of internal medicine at the University of Utah, Salt Lake City, and a research cardiologist at the Intermountain Medical Center Heart Institute.

Hypothyroidism and heart failure

Dr. Noergaard presented a retrospective study of over 1 million Copenhagen-area adults (mean age, 50 years) with no history of heart failure, who had their first thyroid function test. She and her coinvestigators turned to comprehensive Danish national health care registries to determine how many of these individuals were diagnosed with new-onset heart failure within 90 days after their thyroid function test.

Subclinical hypothyroidism was defined by a thyroid-stimulating hormone level greater than 5 mIU/L and a free T₄ of 9-22 pmol/L. Overt hypothyroidism required a TSH greater than 5 mIU/L with a free T₄ less than 9 pmol/L.

Free T₄ predicts atrial fibrillation risk

Dr. Anderson presented a retrospective analysis of 174,914 adult patients in the Intermountain Healthcare EMR database, none of whom were on thyroid replacement at entry. The patients, who were a mean age of 64 years and 65% women, were followed for an average of 6.3 years. Of these, 88.4% had a free T₄ within the normal reference range of 0.75-1.5 ng/dL, 7.4% had a value below the cutoff for normal, and 4.2% had a free T₄ above the reference range.

Upon dividing the patients within the normal range into quartiles based upon their free T₄ level, he and his coinvestigators found that the baseline prevalence of atrial fibrillation was 8.7% in those in quartile 1, 9.3% in quartile 2, 10.5% in quartile 3, and 12.6% in quartile 4. In a multivariate analysis adjusted for potential confounders, the risk of prevalent atrial fibrillation was increased by 11% for patients in quartile 2, compared with those in the first quartile, by 22% in quartile 3, and by 40% in quartile 4.

The incidence of new-onset atrial fibrillation during 3 years of follow-up was 4.1% in patients in normal-range quartile 1, 4.3% in quartile 2, 4.5% in quartile 3, and 5.2% in the top normal-range quartile. The odds of developing atrial fibrillation were increased by 8% and 16% in quartiles 3 and 4, compared with quartile 1.

Serum TSH and free T₃ levels showed no consistent relationship with atrial fibrillation.

The Utah findings confirm in a large U.S. population the earlier report from the Rotterdam Study (J Clin Endocrinol Metab. 2015 Oct;100(10):3718-24).

Dr. Noergaard and Dr. Anderson reported having no financial conflicts regarding their studies, which were carried out free of commercial support.

[email protected]

CHICAGO – The short-term risk of developing heart failure in patients with newly identified hypothyroidism, be it overt or subclinical, is double that of euthyroid individuals, Caroline H. Noergaard, MD, reported at the American Heart Association scientific sessions.

Bruce Jancin/MDedge News

“This is really important clinically. The association with heart failure has previously been shown in both overt and subclinical hyperthyroidism, but it’s actually new knowledge that hypothyroidism is associated with immediate risk of heart failure. And a lot of people have subclinical hypothyroidism,” said Dr. Noergaard, a PhD student in epidemiology at Aalborg (Denmark) University.

Also at the meeting, Jeffrey L. Anderson, MD, reported that free thyroxine levels within the normal reference range were associated in graded fashion with an increased prevalence and incidence of atrial fibrillation in a large Utah study, a finding that provides independent confirmation of an earlier report by investigators from the population-based Rotterdam Study.

“These findings validate those of the Rotterdam Study in a much larger dataset and may have important clinical implications, including a redefinition of the reference range and the target-free T₄ levels for thyroxine replacement therapy,” observed Dr. Anderson, professor of internal medicine at the University of Utah, Salt Lake City, and a research cardiologist at the Intermountain Medical Center Heart Institute.

Hypothyroidism and heart failure

Dr. Noergaard presented a retrospective study of over 1 million Copenhagen-area adults (mean age, 50 years) with no history of heart failure, who had their first thyroid function test. She and her coinvestigators turned to comprehensive Danish national health care registries to determine how many of these individuals were diagnosed with new-onset heart failure within 90 days after their thyroid function test.

Subclinical hypothyroidism was defined by a thyroid-stimulating hormone level greater than 5 mIU/L and a free T₄ of 9-22 pmol/L. Overt hypothyroidism required a TSH greater than 5 mIU/L with a free T₄ less than 9 pmol/L.

Free T₄ predicts atrial fibrillation risk

Dr. Anderson presented a retrospective analysis of 174,914 adult patients in the Intermountain Healthcare EMR database, none of whom were on thyroid replacement at entry. The patients, who were a mean age of 64 years and 65% women, were followed for an average of 6.3 years. Of these, 88.4% had a free T₄ within the normal reference range of 0.75-1.5 ng/dL, 7.4% had a value below the cutoff for normal, and 4.2% had a free T₄ above the reference range.

Upon dividing the patients within the normal range into quartiles based upon their free T₄ level, he and his coinvestigators found that the baseline prevalence of atrial fibrillation was 8.7% in those in quartile 1, 9.3% in quartile 2, 10.5% in quartile 3, and 12.6% in quartile 4. In a multivariate analysis adjusted for potential confounders, the risk of prevalent atrial fibrillation was increased by 11% for patients in quartile 2, compared with those in the first quartile, by 22% in quartile 3, and by 40% in quartile 4.

The incidence of new-onset atrial fibrillation during 3 years of follow-up was 4.1% in patients in normal-range quartile 1, 4.3% in quartile 2, 4.5% in quartile 3, and 5.2% in the top normal-range quartile. The odds of developing atrial fibrillation were increased by 8% and 16% in quartiles 3 and 4, compared with quartile 1.

Serum TSH and free T₃ levels showed no consistent relationship with atrial fibrillation.

The Utah findings confirm in a large U.S. population the earlier report from the Rotterdam Study (J Clin Endocrinol Metab. 2015 Oct;100(10):3718-24).

Dr. Noergaard and Dr. Anderson reported having no financial conflicts regarding their studies, which were carried out free of commercial support.

[email protected]

The novel osteoporosis medication romosozumab received a recommendation from a Food and Drug Administration committee for approval to treat postmenopausal women at high risk of fracture.

In an 18-1 vote, the FDA’s Bone, Reproductive, and Urologic Drugs Advisory Committee agreed that the risk-benefit profile of romosozumab, to be marketed by Amgen as Evenity, was favorable enough to support approval. Relative risk reductions of up to 75%, compared with placebo, and 36%, compared with alendronate, were seen in pivotal clinical trials.

A signal for increased major adverse cardiovascular events (MACE) among those receiving romosozumab had been seen in just one of the clinical trials, with a hazard ratio for MACE of 1.87 for those taking romosozumab, compared with those taking alendronate (95% confidence interval, 1.11-3.14).

Committee members were enthusiastic about the efficacy of the monoclonal antibody, which binds to sclerostin and prevents its inhibiting effect, allowing robust new bone formation. “I want to emphasize the remarkable skeletal efficacy of this drug; truly, it’s better than anything we’ve seen before,” said committee member Sundeep Khosla, MD, professor of medicine and physiology at the Mayo Clinic, Rochester, Minn.

In its application, the sponsor relied on two clinical trials. In the first, 7,180 women with osteoporosis aged 55-90 years were randomized 1:1 to receive romosozumab or placebo for 12 months in a double-blind trial. After this time, participants in each arm received follow-on treatment with denosumab (Prolia) for another 12 months. This study, dubbed Trial 337, followed morphometric vertebral fractures at 12 and 24 months. Morphometric fractures included both symptomatic and asymptomatic fractures.

Those treated with romosozumab had relative risk reductions of new vertebral fractures of 73% and 75%, compared with those given placebo at 12 and 24 months. Absolute risk reductions for vertebral fractures were 1.30% and 1.89% at 1 and 2 years (P less than .001 for both).

The second study, Trial 142, was a double-blind, active-controlled study that included 4,093 women aged 55-90 years with osteoporosis and a history of prior fragility fracture. Participants were randomized 1:1 to receive either romosozumab or alendronate for 12 months, with an additional variable period of alendronate follow-on of at least 12 months for both arms.

For Trial 142, one primary endpoint was morphometric vertebral fractures at month 24. An additional endpoint, clinical fracture, was a composite of symptomatic vertebral fractures and nonvertebral fractures. This second endpoint was assessed at the time of primary analysis, an event-driven cut point that occurred when at least 330 participants experienced a clinical fracture and all participants had completed the 24-month visit.

Bruce Jancin/Frontline Medical News

Almost all the committee’s questioning and discussion centered on this potential increased cardiovascular risk. Amgen, in discussion with the FDA, had agreed to a black box warning designed to wave off prescribing romosozumab to those at increased risk for cardiovascular disease, focusing on those with a history of MI or stroke.

Additionally, the sponsor proposed a postmarketing real-world observational study to track incidence of MACE in those receiving romosozumab, comparing them with those receiving standard of care for osteoporosis.

Several committee members pointed out a problem with the proposed safety mitigation scheme: By conducting a postmarketing observational study for a drug that has a black-box warning to exclude those at high risk for MACE, the chance of detecting an actual cardiovascular safety problem plummets. “This is the textbook example of when observational studies struggle or are virtually guaranteed to fail,” noted Tobias Gerhard, PhD, a pharmacoepidemiologist at Rutgers University, New Brunswick, N.J.

On the other hand, noted several committee members, pausing to conduct a premarketing randomized, controlled trial would keep a beneficial drug away from a population in need. A postmarketing randomized, controlled trial, even a simple trial, still presents challenges, some of the committee acknowledged. Dr. Khosla voiced the opinion that “A randomized, controlled trial is virtually impossible.”

The committee, which was charged with discussing, but not voting on, what additional data should be obtained – and when – to sort out the cardiovascular safety question, was approximately evenly divided in the matter of whether an observational or registry-based trial, or a controlled trial, would be the best path forward.

Committee member Robert A. Adler, MD, put a realistic frame around the debate. “As an endocrinologist, I deal with nuances every day. I really think the kind of clinician who is going to be using this drug is used to dealing with benefits and risks and trying to tailor treatment to a given patient,” said Dr. Adler, professor of internal medicine and epidemiology at Virginia Commonwealth University, Richmond.

In its proposed indication, Amgen defined the population of menopausal women at high risk of fracture as those with a history of osteoporotic fracture, multiple risk factors for fracture, or patients who have failed or are intolerant to other available osteoporosis therapy. Romosozumab would be given as a once-monthly subcutaneous injection of 210 mg for a period of 12 months, to be followed by antiresorptive therapy.

Most of the participants in the clinical trials resided outside the United States, primarily because of the difficulty of recruiting clinical trial participants in the United States, Amgen officials said during their presentation. However, neither the time to the first positively adjudicated MACE nor bone mineral density responses at month 12 differed significantly across the various geographic regions where clinical trial sites were located, said Rachel Wagman, MD, the executive medical director of global clinical development for Amgen. Still, several committee members called for postmarketing data to focus on U.S. patients.

Romosozumab was approved for marketing in Japan on Jan. 8, 2019; approval is also being sought in Europe .

The FDA usually follows the recommendations of its advisory panels.
 

[email protected]

The novel osteoporosis medication romosozumab received a recommendation from a Food and Drug Administration committee for approval to treat postmenopausal women at high risk of fracture.

In an 18-1 vote, the FDA’s Bone, Reproductive, and Urologic Drugs Advisory Committee agreed that the risk-benefit profile of romosozumab, to be marketed by Amgen as Evenity, was favorable enough to support approval. Relative risk reductions of up to 75%, compared with placebo, and 36%, compared with alendronate, were seen in pivotal clinical trials.

A signal for increased major adverse cardiovascular events (MACE) among those receiving romosozumab had been seen in just one of the clinical trials, with a hazard ratio for MACE of 1.87 for those taking romosozumab, compared with those taking alendronate (95% confidence interval, 1.11-3.14).

Committee members were enthusiastic about the efficacy of the monoclonal antibody, which binds to sclerostin and prevents its inhibiting effect, allowing robust new bone formation. “I want to emphasize the remarkable skeletal efficacy of this drug; truly, it’s better than anything we’ve seen before,” said committee member Sundeep Khosla, MD, professor of medicine and physiology at the Mayo Clinic, Rochester, Minn.

In its application, the sponsor relied on two clinical trials. In the first, 7,180 women with osteoporosis aged 55-90 years were randomized 1:1 to receive romosozumab or placebo for 12 months in a double-blind trial. After this time, participants in each arm received follow-on treatment with denosumab (Prolia) for another 12 months. This study, dubbed Trial 337, followed morphometric vertebral fractures at 12 and 24 months. Morphometric fractures included both symptomatic and asymptomatic fractures.

Those treated with romosozumab had relative risk reductions of new vertebral fractures of 73% and 75%, compared with those given placebo at 12 and 24 months. Absolute risk reductions for vertebral fractures were 1.30% and 1.89% at 1 and 2 years (P less than .001 for both).

The second study, Trial 142, was a double-blind, active-controlled study that included 4,093 women aged 55-90 years with osteoporosis and a history of prior fragility fracture. Participants were randomized 1:1 to receive either romosozumab or alendronate for 12 months, with an additional variable period of alendronate follow-on of at least 12 months for both arms.

For Trial 142, one primary endpoint was morphometric vertebral fractures at month 24. An additional endpoint, clinical fracture, was a composite of symptomatic vertebral fractures and nonvertebral fractures. This second endpoint was assessed at the time of primary analysis, an event-driven cut point that occurred when at least 330 participants experienced a clinical fracture and all participants had completed the 24-month visit.

Bruce Jancin/Frontline Medical News

Almost all the committee’s questioning and discussion centered on this potential increased cardiovascular risk. Amgen, in discussion with the FDA, had agreed to a black box warning designed to wave off prescribing romosozumab to those at increased risk for cardiovascular disease, focusing on those with a history of MI or stroke.

Additionally, the sponsor proposed a postmarketing real-world observational study to track incidence of MACE in those receiving romosozumab, comparing them with those receiving standard of care for osteoporosis.

Several committee members pointed out a problem with the proposed safety mitigation scheme: By conducting a postmarketing observational study for a drug that has a black-box warning to exclude those at high risk for MACE, the chance of detecting an actual cardiovascular safety problem plummets. “This is the textbook example of when observational studies struggle or are virtually guaranteed to fail,” noted Tobias Gerhard, PhD, a pharmacoepidemiologist at Rutgers University, New Brunswick, N.J.

On the other hand, noted several committee members, pausing to conduct a premarketing randomized, controlled trial would keep a beneficial drug away from a population in need. A postmarketing randomized, controlled trial, even a simple trial, still presents challenges, some of the committee acknowledged. Dr. Khosla voiced the opinion that “A randomized, controlled trial is virtually impossible.”

The committee, which was charged with discussing, but not voting on, what additional data should be obtained – and when – to sort out the cardiovascular safety question, was approximately evenly divided in the matter of whether an observational or registry-based trial, or a controlled trial, would be the best path forward.

Committee member Robert A. Adler, MD, put a realistic frame around the debate. “As an endocrinologist, I deal with nuances every day. I really think the kind of clinician who is going to be using this drug is used to dealing with benefits and risks and trying to tailor treatment to a given patient,” said Dr. Adler, professor of internal medicine and epidemiology at Virginia Commonwealth University, Richmond.

In its proposed indication, Amgen defined the population of menopausal women at high risk of fracture as those with a history of osteoporotic fracture, multiple risk factors for fracture, or patients who have failed or are intolerant to other available osteoporosis therapy. Romosozumab would be given as a once-monthly subcutaneous injection of 210 mg for a period of 12 months, to be followed by antiresorptive therapy.

Most of the participants in the clinical trials resided outside the United States, primarily because of the difficulty of recruiting clinical trial participants in the United States, Amgen officials said during their presentation. However, neither the time to the first positively adjudicated MACE nor bone mineral density responses at month 12 differed significantly across the various geographic regions where clinical trial sites were located, said Rachel Wagman, MD, the executive medical director of global clinical development for Amgen. Still, several committee members called for postmarketing data to focus on U.S. patients.

Romosozumab was approved for marketing in Japan on Jan. 8, 2019; approval is also being sought in Europe .

The FDA usually follows the recommendations of its advisory panels.
 

[email protected]

The novel osteoporosis medication romosozumab received a recommendation from a Food and Drug Administration committee for approval to treat postmenopausal women at high risk of fracture.

In an 18-1 vote, the FDA’s Bone, Reproductive, and Urologic Drugs Advisory Committee agreed that the risk-benefit profile of romosozumab, to be marketed by Amgen as Evenity, was favorable enough to support approval. Relative risk reductions of up to 75%, compared with placebo, and 36%, compared with alendronate, were seen in pivotal clinical trials.

A signal for increased major adverse cardiovascular events (MACE) among those receiving romosozumab had been seen in just one of the clinical trials, with a hazard ratio for MACE of 1.87 for those taking romosozumab, compared with those taking alendronate (95% confidence interval, 1.11-3.14).

Committee members were enthusiastic about the efficacy of the monoclonal antibody, which binds to sclerostin and prevents its inhibiting effect, allowing robust new bone formation. “I want to emphasize the remarkable skeletal efficacy of this drug; truly, it’s better than anything we’ve seen before,” said committee member Sundeep Khosla, MD, professor of medicine and physiology at the Mayo Clinic, Rochester, Minn.

In its application, the sponsor relied on two clinical trials. In the first, 7,180 women with osteoporosis aged 55-90 years were randomized 1:1 to receive romosozumab or placebo for 12 months in a double-blind trial. After this time, participants in each arm received follow-on treatment with denosumab (Prolia) for another 12 months. This study, dubbed Trial 337, followed morphometric vertebral fractures at 12 and 24 months. Morphometric fractures included both symptomatic and asymptomatic fractures.

Those treated with romosozumab had relative risk reductions of new vertebral fractures of 73% and 75%, compared with those given placebo at 12 and 24 months. Absolute risk reductions for vertebral fractures were 1.30% and 1.89% at 1 and 2 years (P less than .001 for both).

The second study, Trial 142, was a double-blind, active-controlled study that included 4,093 women aged 55-90 years with osteoporosis and a history of prior fragility fracture. Participants were randomized 1:1 to receive either romosozumab or alendronate for 12 months, with an additional variable period of alendronate follow-on of at least 12 months for both arms.

For Trial 142, one primary endpoint was morphometric vertebral fractures at month 24. An additional endpoint, clinical fracture, was a composite of symptomatic vertebral fractures and nonvertebral fractures. This second endpoint was assessed at the time of primary analysis, an event-driven cut point that occurred when at least 330 participants experienced a clinical fracture and all participants had completed the 24-month visit.

Bruce Jancin/Frontline Medical News

Almost all the committee’s questioning and discussion centered on this potential increased cardiovascular risk. Amgen, in discussion with the FDA, had agreed to a black box warning designed to wave off prescribing romosozumab to those at increased risk for cardiovascular disease, focusing on those with a history of MI or stroke.

Additionally, the sponsor proposed a postmarketing real-world observational study to track incidence of MACE in those receiving romosozumab, comparing them with those receiving standard of care for osteoporosis.

Several committee members pointed out a problem with the proposed safety mitigation scheme: By conducting a postmarketing observational study for a drug that has a black-box warning to exclude those at high risk for MACE, the chance of detecting an actual cardiovascular safety problem plummets. “This is the textbook example of when observational studies struggle or are virtually guaranteed to fail,” noted Tobias Gerhard, PhD, a pharmacoepidemiologist at Rutgers University, New Brunswick, N.J.

On the other hand, noted several committee members, pausing to conduct a premarketing randomized, controlled trial would keep a beneficial drug away from a population in need. A postmarketing randomized, controlled trial, even a simple trial, still presents challenges, some of the committee acknowledged. Dr. Khosla voiced the opinion that “A randomized, controlled trial is virtually impossible.”

The committee, which was charged with discussing, but not voting on, what additional data should be obtained – and when – to sort out the cardiovascular safety question, was approximately evenly divided in the matter of whether an observational or registry-based trial, or a controlled trial, would be the best path forward.

Committee member Robert A. Adler, MD, put a realistic frame around the debate. “As an endocrinologist, I deal with nuances every day. I really think the kind of clinician who is going to be using this drug is used to dealing with benefits and risks and trying to tailor treatment to a given patient,” said Dr. Adler, professor of internal medicine and epidemiology at Virginia Commonwealth University, Richmond.

In its proposed indication, Amgen defined the population of menopausal women at high risk of fracture as those with a history of osteoporotic fracture, multiple risk factors for fracture, or patients who have failed or are intolerant to other available osteoporosis therapy. Romosozumab would be given as a once-monthly subcutaneous injection of 210 mg for a period of 12 months, to be followed by antiresorptive therapy.

Most of the participants in the clinical trials resided outside the United States, primarily because of the difficulty of recruiting clinical trial participants in the United States, Amgen officials said during their presentation. However, neither the time to the first positively adjudicated MACE nor bone mineral density responses at month 12 differed significantly across the various geographic regions where clinical trial sites were located, said Rachel Wagman, MD, the executive medical director of global clinical development for Amgen. Still, several committee members called for postmarketing data to focus on U.S. patients.

Romosozumab was approved for marketing in Japan on Jan. 8, 2019; approval is also being sought in Europe .

The FDA usually follows the recommendations of its advisory panels.
 

[email protected]

LOS ANGELES – Mounting evidence suggests that the use of sodium-glucose cotransporter 2 (SGLT-2) inhibitors helps prevent heart failure.

They also may play a role in the treatment of patients with known heart failure (HF), but further studies are required to prove definite treatment benefit.

“These trials enrolled a minority of patients with known heart failure, and, in those subgroups, the drugs seems to reduce the risk for hospitalization, opening the possibility of treatment benefit,” Javed Butler, MD, said at the World Congress on Insulin Resistance, Diabetes & Cardiovascular Disease. “But there were not enough patients to conclude this. If you are treating diabetes with these agents in patients with heart failure, more power to you. But don’t think you are treating heart failure per se until the results of the dedicated heart failure trials come out.”

Good glycemic control has not been shown to affect heart failure outcomes per se, said Dr. Butler, professor and chairman of the department of medicine at the University of Mississippi Medical Center, Jackson.

“People seem to mix the concepts of prevention and treatment together,” he said. “We have now very good evidence across all trials with SGLT-2 inhibitors for prevention of heart failure. But for treatment, we need more data despite favorable early signals.

“Also, these trials include most patients with ischemic heart disease, but we don’t have data on nonischemic etiology for the development of heart failure from these trials,” Dr. Butler added.

The best available data from clinical trials suggest that patients with American College of Cardiology Foundation/American Heart Association heart failure classification stages A and B benefit the most from aggressive treatment to prevent HF.

“Either they have diseases like high blood pressure or diabetes, but their hearts are normal, or, perhaps, their hearts are abnormal, and they develop left ventricular hypertrophy or atrial fibrillation,” he said. “However, if someone is stage C – manifest heart failure – or stage D – advanced heart failure – we need further data on novel therapies to improve their outcomes.”

Dr. Butler emphasized that not all heart failure is associated with atherosclerotic vascular disease. In fact, the Health, Aging, and Body Composition Study showed that the incidence of heart failure increased progressively across age groups, both for those with and without a preceding vascular event (P = .03 and P less than .001, respectively; Eur J Heart Fail. 2014 May;16[5]:526-34). “There’s a whole other world of nonischemic heart failure that we also need to worry about,” he said. “There is a lot of microvascular endothelial dysfunction.”

The combination of heart failure and diabetes is especially lethal. “If you put them together, you’re looking at about a 10-fold higher risk of mortality, which is a horrible prognosis,” Dr. Butler said. “That means that we need to think about prevention and treatment separately.”

Data from the SAVOR-TIMI 53, EXAMINE, and TECOS trials show there is no protective effect of dipeptidyl peptidase–4 inhibitors when it comes to hospitalization for heart failure.

“The other classes of drugs either increase the risk, or we don’t have very good data,” Dr. Butler said. “So far, across the spectrum of therapies for diabetes, the effect on heart failure is neutral and perhaps confers some risk.”

SGLT-2 inhibitors convey a different story.

In the EMPA-REG OUTCOME Trial, one inclusion criterion was established cardiovascular disease (CVD) in the form of a prior MI, coronary artery disease, stroke, unstable angina, or occlusive peripheral artery disease, but not heart failure alone (N Engl J Med. 2015 Nov 26; 373[22]:2117-28). “This was not a heart failure study, so we don’t know what their New York Heart Association class was, or the details of their baseline HF treatment in the minority of patients who were enrolled who had a history of HF,” Dr. Butler cautioned.

However, the trial found that empagliflozin conferred an overall cardiovascular death risk reduction of 38%, compared with placebo. When the researchers assessed the impact of treatment on all modes of cardiovascular death, they found that death from heart failure benefited the most (hazard ratio, 0.32; P = .0008), while sudden death benefited as well. Empagliflozin also had a significant impact on reduced hospitalization for heart failure, compared with placebo (HR, 0.65).

“This is a large enough cohort that you should feel comfortable that this drug is preventing heart failure in those with HF at baseline,” said Dr. Butler, who was not involved with the study. “We can have a debate about whether this is a treatment for heart failure or not, but for prevention of heart failure, I feel comfortable that these drugs do that.”

A subsequent study of canagliflozin and cardiovascular and renal events in type 2 diabetes showed the same result (N Engl J Med. 2017 Aug 17; 377[7]:644-57). It reduced hospitalization for heart failure by 33% (HR, 0.67).

Then came the CVD-REAL study, which found low rates of hospitalization for heart failure and all-cause death in new users of SGLT-2 inhibitors. More recently, DECLARE-TIMI 58 yielded similar results.

“One of the criticisms of these findings is that heart failure characteristics were not well phenotyped in these studies,” Dr. Butler said. “I say it really does not matter. Heart failure hospitalizations are associated with a poor prognosis irrespective of whether the hospitalization occurred in patients without heart failure or in a patient with previously diagnosed heart failure, or whether the patient has reduced or preserved ejection fraction.

“Framingham and other classic studies show us that 5-year mortality for heart failure is about 50%,” he noted. “If you can prevent a disease that has a 5-year mortality of 50%, doesn’t that sound like a really good deal?”

A contemporary appraisal of the heart failure epidemic in Olmstead County, Minn., during 2000-2010 found that the mortality was 20.2% at 1 year after diagnosis, and 52.6% at 5 years after diagnosis. The data include new-onset HF in both inpatient and outpatient settings.

Specifically, new-onset HF hospitalization was associated with a 1-year post discharge mortality of 21.1% (JAMA Intern Med. 2015;175[6]:996-1004). “We cannot ignore prevention of heart failure,” Dr. Butler said. “Also, for treatment, once you get hospitalized for heart failure, the fundamental natural history of the disease changes. There is a 30% cumulative incremental death risk between the second and third hospitalizations.”

Dr. Butler concluded his presentation by noting that five randomized, controlled trials evaluating SGLT-2 inhibitors in HF have been launched, and should help elucidate any effects the drugs may have in treating the condition. They include EMPEROR-Preserved (NCT03057951), EMPEROR-Reduced (NCT03057977), Dapa-HF (NCT03036124), and SOLOIST-WHF (NCT03521934) and DELIVER (NCT03619213).

Dr. Butler disclosed that he has received research support from the National Institutes of Health, the European Union, and the Patient-Centered Outcomes Research Institute. He has also been a consultant for numerous pharmaceutical companies, including Boehringer Ingelheim, Janssen, and AstraZeneca, which sponsored the EMPA-REG, CANVAS, and DECLARE TIMI 58 trials.

[email protected]

LOS ANGELES – Mounting evidence suggests that the use of sodium-glucose cotransporter 2 (SGLT-2) inhibitors helps prevent heart failure.

They also may play a role in the treatment of patients with known heart failure (HF), but further studies are required to prove definite treatment benefit.

“These trials enrolled a minority of patients with known heart failure, and, in those subgroups, the drugs seems to reduce the risk for hospitalization, opening the possibility of treatment benefit,” Javed Butler, MD, said at the World Congress on Insulin Resistance, Diabetes & Cardiovascular Disease. “But there were not enough patients to conclude this. If you are treating diabetes with these agents in patients with heart failure, more power to you. But don’t think you are treating heart failure per se until the results of the dedicated heart failure trials come out.”

Good glycemic control has not been shown to affect heart failure outcomes per se, said Dr. Butler, professor and chairman of the department of medicine at the University of Mississippi Medical Center, Jackson.

“People seem to mix the concepts of prevention and treatment together,” he said. “We have now very good evidence across all trials with SGLT-2 inhibitors for prevention of heart failure. But for treatment, we need more data despite favorable early signals.

“Also, these trials include most patients with ischemic heart disease, but we don’t have data on nonischemic etiology for the development of heart failure from these trials,” Dr. Butler added.

The best available data from clinical trials suggest that patients with American College of Cardiology Foundation/American Heart Association heart failure classification stages A and B benefit the most from aggressive treatment to prevent HF.

“Either they have diseases like high blood pressure or diabetes, but their hearts are normal, or, perhaps, their hearts are abnormal, and they develop left ventricular hypertrophy or atrial fibrillation,” he said. “However, if someone is stage C – manifest heart failure – or stage D – advanced heart failure – we need further data on novel therapies to improve their outcomes.”

Dr. Butler emphasized that not all heart failure is associated with atherosclerotic vascular disease. In fact, the Health, Aging, and Body Composition Study showed that the incidence of heart failure increased progressively across age groups, both for those with and without a preceding vascular event (P = .03 and P less than .001, respectively; Eur J Heart Fail. 2014 May;16[5]:526-34). “There’s a whole other world of nonischemic heart failure that we also need to worry about,” he said. “There is a lot of microvascular endothelial dysfunction.”

The combination of heart failure and diabetes is especially lethal. “If you put them together, you’re looking at about a 10-fold higher risk of mortality, which is a horrible prognosis,” Dr. Butler said. “That means that we need to think about prevention and treatment separately.”

Data from the SAVOR-TIMI 53, EXAMINE, and TECOS trials show there is no protective effect of dipeptidyl peptidase–4 inhibitors when it comes to hospitalization for heart failure.

“The other classes of drugs either increase the risk, or we don’t have very good data,” Dr. Butler said. “So far, across the spectrum of therapies for diabetes, the effect on heart failure is neutral and perhaps confers some risk.”

SGLT-2 inhibitors convey a different story.

In the EMPA-REG OUTCOME Trial, one inclusion criterion was established cardiovascular disease (CVD) in the form of a prior MI, coronary artery disease, stroke, unstable angina, or occlusive peripheral artery disease, but not heart failure alone (N Engl J Med. 2015 Nov 26; 373[22]:2117-28). “This was not a heart failure study, so we don’t know what their New York Heart Association class was, or the details of their baseline HF treatment in the minority of patients who were enrolled who had a history of HF,” Dr. Butler cautioned.

However, the trial found that empagliflozin conferred an overall cardiovascular death risk reduction of 38%, compared with placebo. When the researchers assessed the impact of treatment on all modes of cardiovascular death, they found that death from heart failure benefited the most (hazard ratio, 0.32; P = .0008), while sudden death benefited as well. Empagliflozin also had a significant impact on reduced hospitalization for heart failure, compared with placebo (HR, 0.65).

“This is a large enough cohort that you should feel comfortable that this drug is preventing heart failure in those with HF at baseline,” said Dr. Butler, who was not involved with the study. “We can have a debate about whether this is a treatment for heart failure or not, but for prevention of heart failure, I feel comfortable that these drugs do that.”

A subsequent study of canagliflozin and cardiovascular and renal events in type 2 diabetes showed the same result (N Engl J Med. 2017 Aug 17; 377[7]:644-57). It reduced hospitalization for heart failure by 33% (HR, 0.67).

Then came the CVD-REAL study, which found low rates of hospitalization for heart failure and all-cause death in new users of SGLT-2 inhibitors. More recently, DECLARE-TIMI 58 yielded similar results.

“One of the criticisms of these findings is that heart failure characteristics were not well phenotyped in these studies,” Dr. Butler said. “I say it really does not matter. Heart failure hospitalizations are associated with a poor prognosis irrespective of whether the hospitalization occurred in patients without heart failure or in a patient with previously diagnosed heart failure, or whether the patient has reduced or preserved ejection fraction.

“Framingham and other classic studies show us that 5-year mortality for heart failure is about 50%,” he noted. “If you can prevent a disease that has a 5-year mortality of 50%, doesn’t that sound like a really good deal?”

A contemporary appraisal of the heart failure epidemic in Olmstead County, Minn., during 2000-2010 found that the mortality was 20.2% at 1 year after diagnosis, and 52.6% at 5 years after diagnosis. The data include new-onset HF in both inpatient and outpatient settings.

Specifically, new-onset HF hospitalization was associated with a 1-year post discharge mortality of 21.1% (JAMA Intern Med. 2015;175[6]:996-1004). “We cannot ignore prevention of heart failure,” Dr. Butler said. “Also, for treatment, once you get hospitalized for heart failure, the fundamental natural history of the disease changes. There is a 30% cumulative incremental death risk between the second and third hospitalizations.”

Dr. Butler concluded his presentation by noting that five randomized, controlled trials evaluating SGLT-2 inhibitors in HF have been launched, and should help elucidate any effects the drugs may have in treating the condition. They include EMPEROR-Preserved (NCT03057951), EMPEROR-Reduced (NCT03057977), Dapa-HF (NCT03036124), and SOLOIST-WHF (NCT03521934) and DELIVER (NCT03619213).

Dr. Butler disclosed that he has received research support from the National Institutes of Health, the European Union, and the Patient-Centered Outcomes Research Institute. He has also been a consultant for numerous pharmaceutical companies, including Boehringer Ingelheim, Janssen, and AstraZeneca, which sponsored the EMPA-REG, CANVAS, and DECLARE TIMI 58 trials.

[email protected]

LOS ANGELES – Mounting evidence suggests that the use of sodium-glucose cotransporter 2 (SGLT-2) inhibitors helps prevent heart failure.

They also may play a role in the treatment of patients with known heart failure (HF), but further studies are required to prove definite treatment benefit.

“These trials enrolled a minority of patients with known heart failure, and, in those subgroups, the drugs seems to reduce the risk for hospitalization, opening the possibility of treatment benefit,” Javed Butler, MD, said at the World Congress on Insulin Resistance, Diabetes & Cardiovascular Disease. “But there were not enough patients to conclude this. If you are treating diabetes with these agents in patients with heart failure, more power to you. But don’t think you are treating heart failure per se until the results of the dedicated heart failure trials come out.”

Good glycemic control has not been shown to affect heart failure outcomes per se, said Dr. Butler, professor and chairman of the department of medicine at the University of Mississippi Medical Center, Jackson.

“People seem to mix the concepts of prevention and treatment together,” he said. “We have now very good evidence across all trials with SGLT-2 inhibitors for prevention of heart failure. But for treatment, we need more data despite favorable early signals.

“Also, these trials include most patients with ischemic heart disease, but we don’t have data on nonischemic etiology for the development of heart failure from these trials,” Dr. Butler added.

The best available data from clinical trials suggest that patients with American College of Cardiology Foundation/American Heart Association heart failure classification stages A and B benefit the most from aggressive treatment to prevent HF.

“Either they have diseases like high blood pressure or diabetes, but their hearts are normal, or, perhaps, their hearts are abnormal, and they develop left ventricular hypertrophy or atrial fibrillation,” he said. “However, if someone is stage C – manifest heart failure – or stage D – advanced heart failure – we need further data on novel therapies to improve their outcomes.”

Dr. Butler emphasized that not all heart failure is associated with atherosclerotic vascular disease. In fact, the Health, Aging, and Body Composition Study showed that the incidence of heart failure increased progressively across age groups, both for those with and without a preceding vascular event (P = .03 and P less than .001, respectively; Eur J Heart Fail. 2014 May;16[5]:526-34). “There’s a whole other world of nonischemic heart failure that we also need to worry about,” he said. “There is a lot of microvascular endothelial dysfunction.”

The combination of heart failure and diabetes is especially lethal. “If you put them together, you’re looking at about a 10-fold higher risk of mortality, which is a horrible prognosis,” Dr. Butler said. “That means that we need to think about prevention and treatment separately.”

Data from the SAVOR-TIMI 53, EXAMINE, and TECOS trials show there is no protective effect of dipeptidyl peptidase–4 inhibitors when it comes to hospitalization for heart failure.

“The other classes of drugs either increase the risk, or we don’t have very good data,” Dr. Butler said. “So far, across the spectrum of therapies for diabetes, the effect on heart failure is neutral and perhaps confers some risk.”

SGLT-2 inhibitors convey a different story.

In the EMPA-REG OUTCOME Trial, one inclusion criterion was established cardiovascular disease (CVD) in the form of a prior MI, coronary artery disease, stroke, unstable angina, or occlusive peripheral artery disease, but not heart failure alone (N Engl J Med. 2015 Nov 26; 373[22]:2117-28). “This was not a heart failure study, so we don’t know what their New York Heart Association class was, or the details of their baseline HF treatment in the minority of patients who were enrolled who had a history of HF,” Dr. Butler cautioned.

However, the trial found that empagliflozin conferred an overall cardiovascular death risk reduction of 38%, compared with placebo. When the researchers assessed the impact of treatment on all modes of cardiovascular death, they found that death from heart failure benefited the most (hazard ratio, 0.32; P = .0008), while sudden death benefited as well. Empagliflozin also had a significant impact on reduced hospitalization for heart failure, compared with placebo (HR, 0.65).

“This is a large enough cohort that you should feel comfortable that this drug is preventing heart failure in those with HF at baseline,” said Dr. Butler, who was not involved with the study. “We can have a debate about whether this is a treatment for heart failure or not, but for prevention of heart failure, I feel comfortable that these drugs do that.”

A subsequent study of canagliflozin and cardiovascular and renal events in type 2 diabetes showed the same result (N Engl J Med. 2017 Aug 17; 377[7]:644-57). It reduced hospitalization for heart failure by 33% (HR, 0.67).

Then came the CVD-REAL study, which found low rates of hospitalization for heart failure and all-cause death in new users of SGLT-2 inhibitors. More recently, DECLARE-TIMI 58 yielded similar results.

“One of the criticisms of these findings is that heart failure characteristics were not well phenotyped in these studies,” Dr. Butler said. “I say it really does not matter. Heart failure hospitalizations are associated with a poor prognosis irrespective of whether the hospitalization occurred in patients without heart failure or in a patient with previously diagnosed heart failure, or whether the patient has reduced or preserved ejection fraction.

“Framingham and other classic studies show us that 5-year mortality for heart failure is about 50%,” he noted. “If you can prevent a disease that has a 5-year mortality of 50%, doesn’t that sound like a really good deal?”

A contemporary appraisal of the heart failure epidemic in Olmstead County, Minn., during 2000-2010 found that the mortality was 20.2% at 1 year after diagnosis, and 52.6% at 5 years after diagnosis. The data include new-onset HF in both inpatient and outpatient settings.

Specifically, new-onset HF hospitalization was associated with a 1-year post discharge mortality of 21.1% (JAMA Intern Med. 2015;175[6]:996-1004). “We cannot ignore prevention of heart failure,” Dr. Butler said. “Also, for treatment, once you get hospitalized for heart failure, the fundamental natural history of the disease changes. There is a 30% cumulative incremental death risk between the second and third hospitalizations.”

Dr. Butler concluded his presentation by noting that five randomized, controlled trials evaluating SGLT-2 inhibitors in HF have been launched, and should help elucidate any effects the drugs may have in treating the condition. They include EMPEROR-Preserved (NCT03057951), EMPEROR-Reduced (NCT03057977), Dapa-HF (NCT03036124), and SOLOIST-WHF (NCT03521934) and DELIVER (NCT03619213).

Dr. Butler disclosed that he has received research support from the National Institutes of Health, the European Union, and the Patient-Centered Outcomes Research Institute. He has also been a consultant for numerous pharmaceutical companies, including Boehringer Ingelheim, Janssen, and AstraZeneca, which sponsored the EMPA-REG, CANVAS, and DECLARE TIMI 58 trials.

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Advanced fibrosis affected 5.9% of adults with low-normal thyroid function or subclinical hypothyroidism – more than double the prevalence among adults with strict-normal thyroid function (2.8%; P less than .001), according to the results of a large survey study.

Based on these findings, therapy to improve low thyroid function might help prevent advanced fibrosis secondary to nonalcoholic fatty liver disease, wrote Donghee Kim, MD, PhD, of Stanford University (Calif.), together with his associates in Clinical Gastroenterology and Hepatology.

Prior research has linked low-normal thyroid function with obesity, cardiometabolic diseases, and fractures. For this study, Dr. Kim and his coinvestigators analyzed data from 7,259 adults who lacked major etiologies of chronic liver disease and were included in the National Health and Nutrition Examination Survey between 2007 and 2012.

After accounting for demographic, socioeconomic, and clinical variables, the odds of biopsy-confirmed advanced fibrosis were 100% higher in adults with low-normal thyroid function or subclinical hypothyroidism, compared with adults with strict-normal thyroid function (odds ratio, 2.0; 95% confidence interval, 1.2-3.3). The prevalence and odds of advanced fibrosis was similar in each of these two subgroups. Furthermore, low thyroid function remained strongly linked with advanced fibrosis after accounting for insulin resistance using data from fasting subjects (OR, 2.3; 95% CI, 1.2-4.4).

Previously, Dr. Kim and his coinvestigators found a strong link between biopsy-proven advanced fibrosis and low-normal thyroid function or subclinical hypothyroidism among adults in Korea. “These [new] results are consistent with our previous observations in [an] Asian population, and show their generalizability to the Western world across all ethnicities.”

The researchers did not acknowledge external funding sources. They reported having no conflicts of interest.

SOURCE: Kim D et al. Clin Gastroenterol Hepatol. 2018 Nov 17. doi: 10.1016/j.cgh.2018.11.024.

Advanced fibrosis affected 5.9% of adults with low-normal thyroid function or subclinical hypothyroidism – more than double the prevalence among adults with strict-normal thyroid function (2.8%; P less than .001), according to the results of a large survey study.

Based on these findings, therapy to improve low thyroid function might help prevent advanced fibrosis secondary to nonalcoholic fatty liver disease, wrote Donghee Kim, MD, PhD, of Stanford University (Calif.), together with his associates in Clinical Gastroenterology and Hepatology.

Prior research has linked low-normal thyroid function with obesity, cardiometabolic diseases, and fractures. For this study, Dr. Kim and his coinvestigators analyzed data from 7,259 adults who lacked major etiologies of chronic liver disease and were included in the National Health and Nutrition Examination Survey between 2007 and 2012.

After accounting for demographic, socioeconomic, and clinical variables, the odds of biopsy-confirmed advanced fibrosis were 100% higher in adults with low-normal thyroid function or subclinical hypothyroidism, compared with adults with strict-normal thyroid function (odds ratio, 2.0; 95% confidence interval, 1.2-3.3). The prevalence and odds of advanced fibrosis was similar in each of these two subgroups. Furthermore, low thyroid function remained strongly linked with advanced fibrosis after accounting for insulin resistance using data from fasting subjects (OR, 2.3; 95% CI, 1.2-4.4).

Previously, Dr. Kim and his coinvestigators found a strong link between biopsy-proven advanced fibrosis and low-normal thyroid function or subclinical hypothyroidism among adults in Korea. “These [new] results are consistent with our previous observations in [an] Asian population, and show their generalizability to the Western world across all ethnicities.”

The researchers did not acknowledge external funding sources. They reported having no conflicts of interest.

SOURCE: Kim D et al. Clin Gastroenterol Hepatol. 2018 Nov 17. doi: 10.1016/j.cgh.2018.11.024.

Advanced fibrosis affected 5.9% of adults with low-normal thyroid function or subclinical hypothyroidism – more than double the prevalence among adults with strict-normal thyroid function (2.8%; P less than .001), according to the results of a large survey study.

Based on these findings, therapy to improve low thyroid function might help prevent advanced fibrosis secondary to nonalcoholic fatty liver disease, wrote Donghee Kim, MD, PhD, of Stanford University (Calif.), together with his associates in Clinical Gastroenterology and Hepatology.

Prior research has linked low-normal thyroid function with obesity, cardiometabolic diseases, and fractures. For this study, Dr. Kim and his coinvestigators analyzed data from 7,259 adults who lacked major etiologies of chronic liver disease and were included in the National Health and Nutrition Examination Survey between 2007 and 2012.

After accounting for demographic, socioeconomic, and clinical variables, the odds of biopsy-confirmed advanced fibrosis were 100% higher in adults with low-normal thyroid function or subclinical hypothyroidism, compared with adults with strict-normal thyroid function (odds ratio, 2.0; 95% confidence interval, 1.2-3.3). The prevalence and odds of advanced fibrosis was similar in each of these two subgroups. Furthermore, low thyroid function remained strongly linked with advanced fibrosis after accounting for insulin resistance using data from fasting subjects (OR, 2.3; 95% CI, 1.2-4.4).

Previously, Dr. Kim and his coinvestigators found a strong link between biopsy-proven advanced fibrosis and low-normal thyroid function or subclinical hypothyroidism among adults in Korea. “These [new] results are consistent with our previous observations in [an] Asian population, and show their generalizability to the Western world across all ethnicities.”

The researchers did not acknowledge external funding sources. They reported having no conflicts of interest.

SOURCE: Kim D et al. Clin Gastroenterol Hepatol. 2018 Nov 17. doi: 10.1016/j.cgh.2018.11.024.