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Among asymptomatic people, the prevalence of slightly elevated serum thyroid-stimulating hormone (TSH) levels rises with age. But whether these levels represent subclinical hypothyroidism or age-related changes in the upper limit of normal is unclear. To address this issue, researchers used the NHANES III (National Health and Nutrition Examination Survey III) database. Serum TSH, thyroxine (T4), and antithyroid antibody levels were measured in 16,533 people without known thyroid disease.
TSH levels were >4.5 mIU/L in 15% of older people (age, ≥70) but were this high in only 3% to 8% of younger people. After 2157 people with antithyroid antibodies were excluded, TSH levels remained higher in elders (i.e., 11% prevalence of elevated TSH levels…