Thyroid function, morphology and prevalence of thyroid disease in a population-based study of Danish centenarians.

Objective: To investigate thyroid function, morphology, and autoimmunity in relation to physical function in an unselected population of centenarians.

Methods: A population-based survey. Methods: Denmark. Methods: All persons living in Denmark who celebrated their 100th anniversary during the period April 1, 1995 to May 31, 1996, a total of 276 persons. Methods: Thyroid hormones (TSH, T4, FT4I, T3, FT3I, and T3RU), thyroid autoantibodies (TPOab and Tgab), thyroid volume, activities of daily living according to the Katz Index of ADL.

Results: In all, 207 (75%) of the 276 eligible subjects participated, and 148 agreed to blood tests. Among the participants, 2.9% had previously known hyperthyroidism, and the same proportion had previously known hypothyroidism. The blood tests did not reveal any undiagnosed cases of overt thyroid dysfunction. However 7.2% had a subnormal serum TSH, and 2.9% had an elevated serum TSH; all had normal serum T3 and serum T4 levels. Thyroid autoantibodies were detected in 26 (17.6%) centenarians (11.5% had Tgab and 9.5% had TPOab). Among relatively independent centenarians, low serum T3 was significantly associated with high comorbidity (P = .029), whereas both low serum T3 and thyroid autoantibodies were significantly associated with ADL-dependency (P < .001 and P = .030, respectively). Ultrasonography (n = 50) revealed a small gland with a median volume of 8.3 mL (range 3.2-27.9) compared with an expected volume of 20 mL (14-26) (P < .001). There was no significant relationship to body weight. When examined by ultrasound, only 26% had significant morphological alterations.

Conclusions: Thyroid dysfunction does not seem to be more prevalent among centenarians than among younger old people. Low serum T3 is related to poor physical function and co-morbidity, whereas thyroid autoimmunity is related only to poor physical functioning. Despite atrophy of the thyroid gland, these findings suggest that thyroid function is well preserved in centenarians.