Mild hypothyroidism raises mortality risk among heart failure patients

Chevy Chase, MD—Patients with underlying heart failure are more likely to experience adverse outcomes from mild hypothyroidism, according to a recent study accepted for publication in The Endocrine Society's Journal of Clinical Endocrinology & Metabolism (JCEM).

Hypothyroidism occurs when an underactive thyroid does not produce enough hormones. More than 9.5 million people nationwide have hypothyroidism. People who have thyroid function at the low end of the normal range have subclinical hypothyroidism, also called mild hypothyroidism.

"Our data suggest that mild hypothyroidism may, in fact, be harmful in specific populations, including people with heart failure," said Connie Rhee, MD, MSc, of Brigham and Women's Hospital in Boston. "A 'one-size-fits-all' approach may not be appropriate for assessing risk and determining whether treatment is required for subclinical hypothyroidism."

The retrospective cohort study used data from 14,130 participants in the Third National Health and Nutrition Examination Survey. Using laboratory data, researchers identified 749 participants with hypothyroidism, including 691 with the subclinical form.

Researchers found the condition can have varying impacts on diverse racial and ethnic groups.

"This study is the first to show that African-Americans who have hypothyroidism face a greater risk of death than patients of other racial and ethnic groups," Rhee said. "This elevated risk exists despite the fact that hypothyroidism is less common in the African-American population compared to other groups. More research is needed to confirm these findings and to determine the underlying reasons why hypothyroidism has a differential impact on people of different race and ethnicity."

Other researchers working on the study include: G. Curhan, MD, ScM; E. Alexander, MD; I. Bhan, MD, MPH; and S. Brunelli, MD, MSCE of Harvard Medical School.

The research was supported by grants from the National Institutes of Health's National Institute of Diabetes and Digestive and Kidney Diseases.

The article, "Subclinical Hypothyroidism and Survival: The Effects of Heart Failure and Race," will appear in the June 2013 issue of JCEM.

Founded in 1916, The Endocrine Society is the world's oldest, largest and most active organization devoted to research on hormones and the clinical practice of endocrinology. Today, The Endocrine Society's membership consists of over 16,000 scientists, physicians, educators, nurses and students in more than 100 countries. Society members represent all basic, applied and clinical interests in endocrinology. The Endocrine Society is based in Chevy Chase, Maryland. To learn more about the Society and the field of endocrinology, visit our site at http://www.endo-society.org. Follow us on Twitter at https://twitter.com/#!/EndoMedia.