Association Between Free Thyroxine Levels And Diabetic Retinopathy In Euthyroid Patients With Type 2 Diabetes Mellitus

Objective:This study aimed to evaluate the association between thyroid parameters and diabetic retinopathy（DR）in euthyroid patients with type 2 diabetes mellitus（T2DM）.Methods:In this cross-sectional study,a total of 735 euthyroid patients with T2DM（466men and 269 women;mean age,56.66±10.55 years）were enrolled.Clinical factors were assessed and free triiodothyronine（FT₃）,free thyroxine（FT₄）and thyroid-stimulating hormone（TSH）levels were measured.DR was diagnosed using fundus photography.According to the presence or absence of retinopathy,they were divided into non-diabetic retinopathy group（NDR）289 cases and diabetic retinopathy group（DR）446 cases.The general baseline data and thyroid hormone levels of the two groups were compared,and the FT₃,FT₄,TSH levels of all patients were divided into three groups according to the third percentile,and the difference of Dr prevalence in patients with different thyroid hormone levels was analyzed.Results:Compared with patients without DR,patients with DR exhibited lower FT₃（4.51±0.61 vs 4.63±0.57,P=0.005）and FT₄（15.55±2.05 vs16.14±2.10,P<0.001）and higher TSH（2.27±0.97 vs 2.06±0.95,P=0.005）levels.After adjustment for potential DR risk factors,patients in the highest tertile of plasma FT₄ levels had a 0.520-fold likelihood of developing DR compared with those in the lowest tertile of plasma FT₄ levels（P=0.002）.Conclusion:These findings suggest that low-normal FT₄levels are associated with the prevalence of DR in euthyroid patients with T2DM.