Associations Between Thyroid Hormone Levels,Blood Glucose Control And Diabetic Kidney Disease In Euthyroid Subjects With Type 2 Diabetes Mellitus

Objective:To investigate the relationship between thyroid hormone levels,blood glucose control and diabetic kidney disease（DKD）in euthyroid subjects with type 2diabetes mellitus.Methods:This was a cross-sectional study involving type 2 diabetes mellitus with normal thyroid function aged over 45 years from March 2015 to December 2018.FPG,2h PG,Hb A₁c,TT3,TT4,FT3,FT4,TSH,TPOAb and TGAb in venous plasma and related indicators of DKD were detected.The positive prevalence of thyroid autoimmune antibodies was observed.Univariate ANOVA analysis,Pearson/Spearman correlation analysis and binary logistic regression were used to analyze the relationship between thyroid hormone levels and blood glucose control and diabetic kidney disease in patients whose thyroid autoimmune antibodies were negative.Result:1.Among 260 euthyroid subjects,20（7.7%）were TPOAb or TGAb positive,5（1.9%）were TPOAb positive,18（6.9%）were TGAb positive,and 3（1.2%）were TPOAb and TGAb positive.2.Among 240 subjects with negative thyroid autoimmune antibodies,Hb A₁c was negatively correlated with TT3（r=-0.183,P<0.01）and FT3（r=-0.221,P<0.01）,respectively.According to the level of blood glucose control,Hb A₁c was divided into three groups:Hb A₁c≤7%,7%<Hb A₁c≤9%and Hb A₁c>9%.Univariate ANOVA analysis showed that there was significant statistical difference in FT3 among Hb A₁c groups（P<0.05）.FT3 in Hb A₁c≤7%group was significantly higher than that in7%<Hb A₁c≤9%group（P<0.05）,Hb A₁c>9%group（P<0.01）,and there was no statistical difference in FT3 between 7%<Hb A₁c≤9%group and Hb A₁c>9%group（P>0.05）.3.Among 240 subjects with negative thyroid autoimmune antibodies,the prevalence of diabetic kidney disease increased gradually across the quartiles based on FT3 and TT3 levels.Compared with FT3-Q4（4.10-4.81）group,the prevalence of diabetic kidney disease in FT3-Q1（2.94-3.52）and FT3-Q2（3.52-3.84）was significantly increased（X²=9.636,5.227;P<0.01,0.05）.Compared with TT3-Q4（1.53-1.94）group,the prevalence of diabetic kidney disease in TT3-Q1（0.33-1.27）group was significantly increased（X²=7.557;P<0.01）.Logistic regression analysis showed that the adjusted odds ratio of DKD in FT3-Q1 and FT3-Q2 groups was significantly higher than that in FT3-Q4 group（OR 5.132[95%CI,1.561-16.872],P<0.01;OR3.775[95%CI,1.131-12.596],P<0.05）.The prevalence of DKD did not differ significantly among FT4,TT4,and TSH groups.Conclusion:1.The positive prevalence of thyroid autoimmune antibody was 7.7%in euthyroid subjects with type 2 diabetes mellitus,and there was no significant difference between genders and age groups.2.The level of FT3 in euthyroid subjects with type 2 diabetes mellitus decreased when the blood glucose control was poor.The level of FT3 can reflect the level of blood glucose control and predict the severity of diabetes mellitus.3.The low level of FT3 in normal range was significantly correlated with the high prevalence of diabetic kidney disease,which may be an independent risk factor for diabetic kidney disease.