People with moderate subclinical hypothyroidism (SCH), a condition in which the thyroid is mildly underactive, are at increased risk of death, according to data to be presented on Oct. 4, 2008 at the 79th Annual Meeting of the American Thyroid Association (ATA) in Chicago, Ill.

SCH – indicated by a raised thyroid-stimulating hormone (TSH) but normal thyroxine level – has minor or no symptoms of overt hypothyroidism disease and is detectable only through blood tests. SCH is common among the elderly, particularly elderly women. Although it is known that hypothyroidism increases risk for cardiovascular disease and mortality, data to date regarding the relationship between SCH and mortality and cardiovascular disease is inconclusive.

Using the Preventive Cardiology Information System (PreCIS), a team of researchers from the Cleveland Clinic studied more than 6,000 patients seen at the Prevention Cardiology Clinic. Researchers evaluated TSH at each patient’s initial visit and linked with demographic and laboratory data. Mortality was measured six years later. Survival was compared amongst subjects with varying levels of TSH.

Researchers found that patients with either hypothyroidism (> 10.0 µU/ml) or moderate SCH (6.0-10.0 µU/ml) were at increased risk of dying than patients with normal thyroid function. Mild SCH (3.0-6.0 µU/ml) was not found to increase patients’ risk of dying. Researchers also found that hypothyroidism and moderate SCH increased patients’ risk of developing cardiovascular disease.

“These data demonstrate that the previously reported correlation between hypothyroidism and cardiovascular disease and mortality is extended to a population who is at high risk for cardiovascular disease, but whose cardiovascular risk factors are also pretty aggressively treated. The data also demonstrate that patients with moderate SCH are at increased risk of death and poor cardiovascular health. These findings suggest that patients with moderate SCH should be treated with L-thyroxine therapy as this treatment may reduce mortality,” said Dr. Mario Skugor, principle investigator of the study.

About the American Thyroid Association (ATA)
The American Thyroid Association (ATA) is the lead organization in promoting thyroid health and understanding thyroid biology. The ATA values scientific inquiry, clinical excellence, public service, education, collaboration, and collegiality.

A non-profit medical society founded in 1923, the ATA fulfills its mission through supporting excellence and innovation in research, clinical care, education, and public health. ATA members are physicians and scientists who work to enhance the understanding of thyroid physiology and pathophysiology, improve the diagnosis and treatment of thyroid diseases, and promote the education of physicians, patients, and the public about thyroid disorders.

Thyroid diseases are among the most common disorders of the endocrine system, affecting almost 13 million Americans alone. The ATA has extensive online information for patients on thyroid disease (in English and Spanish) serving the clinician as a resource for patients and the public who look for reliable information on the internet.

Distribution of information regarding research presented at ATA meetings is thought to be of interest to the public, however, this does not imply official endorsement by the ATA.

Source: American Thyroid Association