Abstract
BACKGROUND: Thyroid hormone levels are associated with the distribution of body components in humans. OBJECTIVE: This study aimed to investigate the associations between thyroid hormone (TH) levels, central sensitivity to THs, and body composition in overweight and obese patients with euthyroid type 2 diabetes mellitus (T2DM). METHODS: This cross-sectional study included 1215 euthyroid T2DM patients (721 men and 494 women) aged 20-80 years. The thyroid hormone sensitivity indices included the thyroid feedback quartile-based index (TFQI), thyrotroph T3 resistance index (TT3RI), thyrotroph T4 resistance index (TT4RI), and thyroid-stimulating hormone index (TSHI). The appendicular fat ratio, trunk fat ratio, android fat ratio, gynoid fat ratio, and appendicular skeletal muscle mass (ASM) were measured via dual-energy X-ray absorptiometry. RESULTS: The data revealed a greater proportion of subjects with impaired central sensitivity to THs in the obese group. TFQI(FT4) and TFQI(FT3) levels were positively correlated with the upper limb fat ratio, lower limb fat ratio, gynoid fat ratio, and total fat ratio. TSHI was positively correlated with body mass index (BMI), upper limb fat ratio, lower limb fat ratio, trunk fat ratio, android fat ratio, gynoid fat ratio, total fat ratio, and appendicular skeletal muscle mass index (ASMI) in women. In men, TSHI was only positively correlated with upper limb fat ratio, lower limb fat ratio, and total fat ratio. Logistic regression analysis indicated that TT3RI and TFQI(FT3) were independently and positively associated with central obesity and low muscle mass in overweight and obese men. No significant differences were found among the women. CONCLUSION: THs central sensitivity is related to the body composition of euthyroid T2DM patients. Specifically, high levels of TT3RI and TFQI(FT3) are associated with central obesity and low muscle mass in T2DM men with overweight and obesity.