Predictive Effect of FT3 Within the Euthyroid Range on HDL-C in Patients With Type 2 Diabetes: A Cross-Sectional Analysis of Inpatients in China.

Abstract

Background: Evidence for assessing the relationship between free triiodothyronine (FT3) and high-density lipoprotein cholesterol (HDL-C) remains limited. Therefore, the purpose of our study is to evaluate the relationship between FT3 and HDL-C in patients with type 2 diabetes.

Methods: From June 2022 to October 2023, 3011 patients with normal thyroid function and diagnosed with type 2 diabetes mellitus (T2DM) were collected continuously and non-selectively in a Chinese hospital. Then, we used a logistic regression model to explore the relationship between FT3 and HDL-C. Smooth curve fitting is used to identify the nonlinear relationship between FT3 and HDL-C.

Results: After adjusting for the influence of relevant factors, FT3 and HDL-C were negatively correlated -0.02 (-0.04, -0.00; p = 0.0162). There is also a nonlinear relationship between FT3 and HDL-C, with an inflection point of 3.48 pmol/L for FT3 (P for log- likelihood ratio test = 0.044).

Conclusion: This study shows that there is a negative correlation and nonlinear relationship between FT3 and HDL-C in the Chinese population with diabetes. When FT3 is between 2.76-3.48 pmol/L, HDL-C tends to a stable state; When FT3 is between 3.48-6.45 pmol/L, HDL-C decreases with the increase of FT3 concentration (According to the reference range used by our hospital, the normal value of serum FT3 is 2.76-6.45 pmol/L). These findings suggest that maintaining FT3 within the range of 2.76 to 3.48 pmol/L may be most beneficial for mitigating the progression of cardiovascular disease in patients with T2DM.