Subclinical Thyroid Dysfunction is a Risk for Heart Disease
Few large studies have looked at the connection between thyroid dysfunction and heart disease, and in particular, the question of whether subclinical hypothyroidism is a risk factor for development of heart disease. Reporting in the Nov. 28, 2005 issue of the Archives of Internal Medicine, researchers looked at the TSH and Free T4 levels of more than 2100 patients. What they found was that patients with subclinical hypothyroidism had a much higher rate of heart disease than those with normal thyroid levels. Patients with subclinical hyperthyroidism, however, had no adverse outcomes. This led researchers to conclude that subclinical hypothyroidism may be an independent risk factor for heart disease.
Subclinical Hypothyroidism is a Risk for Congestive Heart Failure in Seniors
Asymptomatic hypothyroidism -- in which patients have elevated TSH, normal thyroxine (T4), and few if any symptoms -- is more common as we get older. While subclinical hypothyroidism is known to have some effects on cardiac function, blood pressure, and cholesterol level, researchers have done limited studies on the relationship between subclinical hypothyroidism and heart disease outcomes and death. Reporting in the Nov. 28, 2005 issue of the Archives of Internal Medicine, more than 2700 older patients were studied; they were age 70 to 79 . Their TSH was measured, and they were followed for four years, to evaluate congestive heart failure, coronary heart disease, stroke, peripheral arterial disease, and cardiovascular-related and total mortality. Subclinical hypothyroidism was defined as normal T4, but TSH level of 4.5 or greater. The group was also subclassified according to TSH levels of 4.5-6.9, 7.0-9.9, and greater than 10.0. Subclinical hypothyroidism was found in 12.4% of the participants. Compared to patients with normal thyroid function, congestive heart failure occurred more often in those with a TSH level of 7.0 or hgher, but not among those with 4.5-6.9 TSH. The researchers did not find an increased risk of coronary heart disease, stroke, peripheral arterial disease, or cardiovascular-related or total mortality in the elderly patients with subclinical hypothyroidism. The researchers concluded that subclinical hypothyroidism is associated with an increased risk of congestive heart failure among older adults age 70+ who had a TSH level of 7.0 or greater, but not with other heart disease problems or death.
Sources:
Rodondi, Nicolas MD, MAS; et. al. "Subclinical Hypothyroidism and the Risk of Heart Failure, Other Cardiovascular Events, and Death." Arch Intern Med. 2005;165:2460-2466. Vol. 165 No. 21, November 28, 2005. Abstract online
Walsh, John P. MBBS, PhD; et. al. "Subclinical Thyroid Dysfunction as a Risk Factor for Cardiovascular Disease," Arch Intern Med. 2005;165:2467-2472. Vol. 165 No. 21, November 28, 2005, Abstract online
Mary Shomon, About.com's Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including "The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss," "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know," "Living Well With Graves' Disease and Hyperthyroidism," "Living Well With Autoimmune Disease," "Living Well With Chronic Fatigue Syndrome and Fibromyalgia," and the "Thyroid Guide to Fertility, Pregnancy and Breastfeeding Success." Click here for more information on Mary Shomon.
