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

OBJECTIVES: To investigate thyroid function, morphology, and autoimmunity i n relation to physical function in an unselected population of centenarians . DESIGN: A population-based survey. SETTING: Denmark. PARTICIPANTS: All persons living in Denmark who celebrated their 100th anni versary during the period April 1, 1995 to May 31, 1996, a total of 276 per sons. MAIN OUTCOME MEASUREMENTS: Thyroid hormones (TSH, T4, FT4I, T3, FT3I, and T 3RU), thyroid autoantibodies (TPOab and Tgab), thyroid volume, activities o f daily living according to the Katz Index of ADL. RESULTS: In all, 207 (75%) of the 276 eligible subjects participated, and 1 48 agreed to blood tests. Among the participants, 2.9% had previously known hyperthyroidism, and the same proportion had previously known hypothyroidi sm. The blood tests did not reveal any undiagnosed cases of overt thyroid d ysfunction. However 7.2% had a subnormal serum TSH, and 2.9% had an elevate d serum TSH; all had normal serum T3 and serum T4 levels. Thyroid autoantib odies were detected in 26 (17.6%) centenarians (11.5% had Tgab and 9.5% had TPOab). Among relatively independent centenarians, low serum T3 was signif icantly associated with high comorbidity (P = .029), whereas both low serum T3 and thyroid autoantibodies were significantly associated with ADL-depen dency (P < .001 and P = .030, respectively). Ultrasonography (n = 50) revea led a small gland with a median volume of 8.3 mt (range 3.2-27.9) compared with an expected volume of 20 mt (14-26) (P < .001). There was no significa nt relationship to body weight. When examined by ultrasound, only 26% had s ignificant morphological alterations. CONCLUSIONS: Thyroid dysfunction does not seem to be more prevalent among c entenarians 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, t hese findings suggest that thyroid function is well preserved in centenaria ns.