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Unrecognized thyroid dysfunction is common in the general population

(July 2002)

The background of the study. Thyroid disease is common among patients who seek medical care, and presumably also in the population at large. This substudy of the 1988 to 1994 National Health and Nutrition Examination Survey assessed thyroid function in many people in the United States.

How the study was done. The study subjects were 17,353 people aged ≥12 years living in all 50 U.S. states. Demographic, socioeconomic, and health information was obtained, and serum was collected for measurements of thyrotropin (TSH), thyroxine, and thyroid peroxidase and thyroglobulin antibodies. The results were extrapolated to the US population as a whole.

The results of the study. The estimated prevalence of hypothyroidism and hyperthyroidism in the total population in 1988 to 1994 was 4.6 percent (9,597,742 people) and 1.3 percent (2,610,097), respectively. Most of the people had subclinical hypothyroidism or subclinical hyperthyroidism (normal serum thyroxine and abnormal serum TSH values.) The frequency of hypothyroidism was lower in blacks (1.7 percent) than in whites, Hispanics, or other groups (4.1 to 5.1 percent). The frequency of hyperthyroidism was similar in these groups (0.7 to 1.4 percent).

The frequency of high serum TSH values (>4.5 mU/L) was approximately 2 percent among the 30- to 39-year-old people, 5 percent among the 50- to 59-year-old people, and 12 percent among the 70- to 79-year-old people. In contrast, the frequency of low serum TSH values (<0.4 mU/L) did not increase with age.

The serum concentrations of antithyroid peroxidase and antithyroglobulin antibodies were high in 11.3 and 10.4 percent of the people, respectively. The percentage of black people in whom concentrations were high was approximately 50 percent lower than in the white or Hispanic people. The frequency of high values increased with age, and was two times higher in women than in men.

The conclusions of the study. Many Americans have unrecognized thyroid dysfunction, and its frequency varies among different racial/ethic groups.

The original article. Hollowell JG, Staehling NW, Flanders WD, Hannon WH, Gunter EW, Spencer CA, Braverman LE. Serum TSH, T4, and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab 2002;87:489-99.

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