Sensitivity to thyroid hormone and risk of components of metabolic syndrome in a Chinese euthyroid population

Introduction: To evaluate the association of sensitivity to thyroid hormone with metabolic syndrome (MetS) and its components in a Chinese euthyroid population. Methods: A total of 3573 participants from Pinggu Metabolic Disease Study were analyzed. Serum-free triiodothyronine (FT3), free thyroxine (FT4), thyrotropin (TSH), total adipose tissue (TAT), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT) area of abdominal, and lumbar skeletal muscle area (SMA) were measured. Central thyroid hormone resistance was calculated by the Thyroid Feedback Quantile-based Index (TFQI) and Chinese-referenced Parametric TFQI (PTFQI), Thyrotroph T4 Resistance Index (TT4RI) and TSH Index (TSHI). Peripheral thyroid hormone resistance was assessed by FT3/FT4 ratio. Results: Higher values of TSHI (odds ratio [OR] = 1.167, 95% confidence interval [CI]: 1.079–1.262, p <.001), TT4RI (OR = 1.115, 95% CI: 1.031–1.206, p =.006), TFQI (OR = 1.196, 95% CI: 1.106–1.294, p <.001), PTFQI (OR = 1.194, 95% CI: 1.104–1.292, p <.001), and lower values of FT3/FT4 ratio (OR = 0.914, 95% CI: 0.845–0.990, p =.026) were associated with MetS. Increased levels of TFQI and PTFQI were associated with abdominal obesity, hypertriglyceridemia, and hypertension. Increased levels of TSHI and TT4RI were associated with hypertriglyceridemia, abdominal obesity, low high-density lipoprotein cholesterol. Reduced levels of FT3/FT4 ratio were associated with hyperglycemia, hypertension, and hypertriglyceridemia. The levels of TSHI, TFQI, and PTFQI were negatively related to SMA and positively related to VAT, SAT, and TAT (all p <.05). Conclusions: Reduced thyroid hormone sensitivity was associated with MetS and its components. Impaired thyroid hormone sensitivity might affect the distribution of adipose tissue and muscle.