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African Americans with hypothyroidism face an increased risk of death, and in patients with congestive heart failure (CHF), even mild underactive thyroid disease raises mortality risk, a retrospective cohort study found.

Hypothyroidism overall was associated with greater mortality in black participants (adjusted HR 1.44, 95% CI 1.03-2.03) but not in nonblacks (HR 0.95, 95% CI 0.83-1.08, P=0.03 for the interaction), according to Connie Rhee, MD, MSc, of Boston's Brigham and Women's Hospital, and colleagues. A trend toward subclinical hypothyroidism and early death was seen in African Americans, but it did not reach statistical significance (HR 1.51, 95% CI 1.05-2.17, P=0.07).

In addition, subclinical hypothyroidism was associated with an increased risk for death in CHF patients but not in those without CHF (adjusted HRs 1.44 [95% CI 1.01-2.06] and 0.97 [95% CI 0.85-1.11], respectively, P=0.03 for the interaction), Rhee and colleagues wrote in the Journal of Clinical Endocrinology & Metabolism.

The analysis showed the same association for hypothyroidism overall in CHF patients (adjusted HR 1.47, 95%CI 1.05-2.05) but not in those without CHF (adjusted HR 0.95, 95% CI 0.83-1.09, P=0.01 for the interaction), they wrote.

The new analysis of data from the Third National Health and Nutrition Examination Survey (NHANES III) adds to the evidence that subclinical hypothyroidism has prognostic significance in heart failure patients, Rhee said.

It is also the first study to link hypothyroidism to an increased risk of death in blacks, but not other races, she and her colleagues wrote.

Several earlier studies have suggested a link between subclinical hypothyroidism and poor outcomes in heart failure patients, but other studies have failed to show the association.

Prior studies have also suggested that African Americans tend to have lower levels of thyroid stimulating hormone (TSH), which is considered the most sensitive measure of thyroid function. Blacks have a lower incidence of hypothyroidism compared with other races, but it has not been clear if they have worse outcomes when they do develop underactive thyroid disease, Rhee explained.

To explore their hypothesis that hypothyroidism and subclinical disease increase death risk among CHF patients and blacks, Rhee and colleagues examined NHANES III data on 14,130 controls and 749 patients with hypothyroidism -- including 691 people with subclinical hypothyroidism.

The findings in the nationally representative sample of nonhospitalized CHF patients and African Americans were robust across multiple secondary analyses, as well as sensitivity analyses that adjusted for cardiovascular medication and excluded participants on baseline thyroid drugs.

The results suggest that a one-size-fits-all approach to assessing whether patients with mild hypothyroidism need treatment could be detrimental to certain populations, Rhee told 木瓜直播.

"It is estimated that between 9.5 and 10 million people in the U.S. have hypothyroidism, and a significant percentage have a milder form of the condition that is considered subclinical," she said. "There is still a lot of controversy about whether treatment of this milder form is warranted."

A big unanswered question is whether treating subclinical hypothyroidism can impact survival times in patients with congestive heart failure, Rhee said, adding that more research is also needed to determine why African Americans with hypothyroidism have worse outcomes.

"We need more studies to understand the mechanisms behind these differences," she said.

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