Abstract:Objective: To evaluate the relationships of thyroid hormone levels and thyroid hormone sensitivity with simplified insulin sensitivity indexes in euthyroid individuals. Methods: The study enrolled 4 909 euthyroid individuals who underwent a health examination at The First Hospital of China Medical University between January 2017 and December 2018. Thyroid feedback quantile-based index (TFQI) and free triiodothyronine to free thyroxine ratio (FT3/FT4) were calculated to reflex thyroid hormone sensitivity. Simplified insulin sensitivity indexes included triglyceride glucose index (TyG) , TyG-body mass index, TyG-waist circumference, triglyceride to high-density lipoprotein-cholesterol ratio, visceral adiposity index and lipid accumulation product. Results: Multiple linear regression analyses showed that FT3/FT4, FT3 and thyroid stimulating hormone (TSH) were positively associated with TyG (β=1.651, 0.122 and 0.060, respectively) ; FT4was negatively associated with TyG (β=-0.026, all P=0.000) . Logistic regression showed that, with 1 SD increase in FT3/FT4, the odds ratio for high TyG, which was defined as the highest quartiles was 1.282, 95%confidence interval was from 1.193 to 1.379. The risk for high TyG increased with the increases of FT3 and TSH, and decreased with the increase of FT4. Other simplified insulin sensitivity indexes showed similar relationships with the above thyroid parameters. These results were remained when we grouped people according to gender, body mass index, and the levels of thyroid autoantibodies. TFQI was only associated with a part of simplified insulin sensitivity indexes. Conclusion: Simplified insulin sensitivity indexes are associated with thyroid hormone sensitivity and serum hormone levels. They provided an easy tool for evaluating the relationships between thyroid function and insulin sensitivity.
