Impaired Sensitivity to Thyroid Hormones is Associated with High Insulin Resistance Levels in the Euthyroid Chinese Population

Abstract Background : The association between thyroid hormones sensitivity and insulin resistance (IR) remains unknown. This study was designed to analyze the relationship between sensitivity to thyroid hormones and IR stratified by different levels of obesity. Methods : 32478 euthyroid participants were included and they were divided into three groups according to the body mass index (BMI): normal weight (n=20200), overweight (n=10178) and obesity (n=2100). We used The Thyroid Feedback Quantile-based Index (TFQI), The TSH Index (TSHI), the Thyrotrophic T4 Resistance Index (TT4RI) to represent thyroid hormones sensitivity and used Triglyceride-Glucose (TyG) Index, the Atherogenic Index of Plasma (AIP), The Metabolic Score for Insulin Resistance (METS-IR) to represent IR. The association between thyroid hormones sensitivity and IR were analyzed by linear regression and logistic regression. Results: Linear regression analysis revealed that TFQI, TSHI and TT4RI were positively associated with TyG, AIP and METS-IR. Logistic regression showed that in the normal weight group, the odds ratios (ORs) for having high TyG in the highest quartiles of the TFQI, TSHI, and TT4RI were 1.430 (95% CI: 1.288,1.587); 1.537 (95% CI: 1.388,1.703); 1.518 (95% CI: 1.370,1.682) respectively (all p <0.001) compared with the lowest quartiles of the TFQI, TSHI, and TT4RI; In the overweight group, the ORs for having high TyG in the highest quartiles of the TFQI, TSHI, and TT4RI were 1.269 (95% CI:1.104,1.459); 1.363 (95% CI:1.186,1.566); 1.353 (95% CI:1.177,1.555) respectively (all p < 0.001); In the obesity group, the ORs for having high TyG in the highest quartiles of the TFQI, TSHI, and TT4RI were 1.298 (95% CI:0.951,1.774) ( p =0.101); 1.454 (95% CI:1.065,1.989) ( p =0.05); 1.455 (95% CI:1.066,1.991) ( p =0.05) respectively. AIP and METS-IR yielded roughly similar results. Conclusion : In euthyroid adults, reduced sensitivity to thyroid hormones was associated with high levels of IR. Our study provides insight for further exploring the pathogenesis of metabolic syndrome as well as guidance for its treatment.