Purpose: This study aims to investigate the relationship between thyroid and type 1 diabetic nephropathy (T1DN) in euthyroid populations, focusing on thyroid hormone sensitivity.
Methods: A cross-sectional study was conducted between January 2016 and December 2021, including 357 euthyroid patients with type 1 diabetes mellitus (T1DM). Parameters representing thyroid hormone sensitivity were assessed, including the thyroid feedback quantile-based index (TFQI), parameter thyroid feedback quantile index (PTFQI), thyroid stimulating hormone index (TSHI), thyrotropin thyroxine resistance index (TT4RI), and free triiodothyronine/free thyroxine (FT3/FT4). Logistic regression and restricted cubic spline regression were performed to detect the association between thyroid hormone sensitivity and the risk of T1DN.
Results: The study found a negative correlation between the risk of T1DN and FT3/FT4 in euthyroid T1DM patients (OR 0.71, 95% CI 0.51– 0.97, P < 0.01). PTFQI (P< 0.05), TSHI (P< 0.05), and TT4RI (P< 0.01) showed an M-shaped nonlinear relationship with the risk of T1DN. Elevated risk of T1DN was associated with PTFQI, TSHI, and TT4RI values outside the range of zero, 2.3– 3.88, and 27.56– 32.19, respectively.
Conclusion: This study confirms the relationship between impaired thyroid hormone sensitivity and the risk of T1DN in euthyroid patients. It emphasizes the importance of evaluating thyroid hormone sensitivity in T1DM patients, even when their thyroid function appears normal, to promptly prevent the occurrence of T1DN.

Keywords: euthyroid, sensitivity to thyroid hormones, type 1 diabetic nephropathy