Diabetic kidney disease (DKD) is a major complication of type 2 diabetes mellitus (T2DM), and the role of thyroid hormones in kidney function remains unclear. Limited data exist on the association between free triiodothyronine (FT3) levels and renal parameters in individuals with T2DM who have normal thyroid function.

A cross-sectional analysis published in Diabetes & Metabolic Syndrome Clinical Research & Reviews evaluated the relationship between FT3 levels and kidney function in patients with T2DM. The study included 3,124 patients with normal thyroid function who were consecutively enrolled between June 2022 and October 2023 at a Chinese hospital. Logistic regression models were used to assess the association between FT3 and estimated glomerular filtration rate (eGFR), and smooth curve fitting was applied to assess potential nonlinear relationships.

The analysis showed a positive association between FT3 levels and eGFR after adjustment for relevant factors (β 2.34; 95% confidence interval 0.27 to 4.41; P=0.0267). A nonlinear relationship between FT3 and eGFR was also observed. Inflection points were identified at FT3 levels of 3.47 pmol/L (P=0.002) and 5.17 pmol/L (P=0.012).

These findings indicate that FT3 levels between 3.47 and 5.17 pmol/L were associated with more stable eGFR values in patients with T2DM, based on the observed relationship in this analysis.