The Effect of Thyroid Hormones on Sarcopenia in a Chinese Elderly Population

Abstract Purpose Sarcopenia is a common disease in the elderly. The change of hormone levels with age is proposed to be involved in the pathogenesis of sarcopenia, but the effect of thyroid hormones (THs) on sarcopenia is unclear. In this study, we aimed to analyze the effect of THs on sarcopenia.Methods Total 309 elderly subjects (122 females and 187 males) with an average age of 85.19 ± 7.8 years were enrolled. Participants were divided into four groups (non-sarcopenia, sarcopenia, possible sarcopenia and serve sarcopenia) based on the consensus of the Asian Working Group for Sarcopenia in 2019. Serum levels of total triiodothyronine (TT3), free triiodothyronine (FT3), thyroxine (T4), free thyroxine (FT4), thyroid stimulating hormone (TSH), reverse triiodothyronine (rT3), and thyroxine-binding globulin (TBG) were measured. Muscle mass was measured by multifrequency bioelectrical impedance analysis (BIA). Grip was measured by spring-type dynamometer. Walking speed was represented by 6-minute walk test. Results The levels of FT3, TT3 and TSH were significantly different in four groups. Partial correlation analysis (adjusted by age and gender) indicated that FT3, TT3 and TSH had significant correlation with hand grip. In addition, TT3 was correlated with walking speed. Regression analysis showed that TT3 was a protective factor for sarcopenia and hand grip, and TSH was a protective factor for severe sarcopenia. Conclusions T3 plays a protective role in sarcopenia, and this effect is achieved by affecting muscle strength but not muscle mass and gait speed. Moreover, compared with FT3, this study suggested that TT3 was more suitable to evaluate the relationship between thyroid and sarcopenia in elderly.