Association between sensitivity to thyroid hormone indices and type 2 diabetic microvascular complications in euthyroid patients

The correlation between thyroid hormone (TH) sensitivity and microvascular complications of type 2 diabetes mellitus (T2DM) remains uncertain. This study aimed to explore the association between TH sensitivity and the risk of diabetic kidney disease (DKD), diabetic retinopathy (DR), and diabetic neuropathy (DNP) in euthyroid T2DM patients. This study included a total of 946 hospitalized T2DM patients and calculated their sensitivity to the TH index, and each patient completed screenings for DKD, DR, and DNP. Multivariate logistic regression, generalized additive modeling, and subgroup analysis were used to assess the association between TH index sensitivity and the risks of DKD, DR, and DNP. After adjusting for confounding factors, a significant linear correlation was observed between the sensitivity of the thyroid feedback quartile index 3 (TFQI3) and DKD risk. However, the sensitivities of thyroid-stimulating hormone index (TSHI), thyrotropin thyroxine resistance index (TT4RI) and partial thyroid feedback quartile index (PTFQI) exhibited nonlinear correlations with the risk of developing DKD. The effect sizes to the left of the inflection point for TSHI, TT4RI and PTFQI were (odd ratio [OR] = 0.53, 95% confidence interval [CI]: 0.288-0.977), (OR = 0.863, 95%Cl: 0.751-0.992) and (OR = 0.007, 95%Cl: 0-0.724), respectively. However, there was no significant correlation between TH index sensitivity and DR/DNP risk. This study provides valuable insights into the relationship between TH sensitivity and the risks of DKD, DR, and DNP, with substantial clinical implications for individual prediction among T2DM patients.