Higher free thyroxine levels are associated with sarcopenia in elderly Koreans

BackgroundSkeletal muscle is a major target of thyroid hormone action. Although sarcopenia is associated with adverse health outcomes in the elderly, few studies have examined the association between sarcopenia and thyroid hormone levels in elderly Asians. We investigated the relationship between thyroid hormone levels and sarcopenia in elderly Koreans.Methods658 individuals (324 males and 334 females) ≥60 years old who visited the Health Screening and Promotion Center at Ajou University Hospital were recruited for the study. Whole-body dual-energy X-ray absorptiometry was performed, and gait speed and hand grip strength were measured. The rate and odds ratios for sarcopenia were calculated for free thyroxine (fT4) and thyroid stimulating hormone (TSH) levels.ResultsThe fT4 concentration was negatively associated with muscle mass in males (r2 = 0.031, p = 0.001) and females (r2 = 0.019, ps = 0.011). The highest rate of sarcopenia occurred in the highest fT4 quartile in males and females. However, no significant differences were found among TSH quartiles in either sex. TSH was not significantly associated with the risk of sarcopenia in males or females, whereas the fT4 concentration was associated with the risk of sarcopenia in both sexes.ConclusionsHigher fT4 levels, not lower TSH levels might have an adverse effect on sarcopenia especially in elderly people.