Correlation Between Thyroid Hormone And Microvascular Complications In Euthyroid Patients With Type 2 Diabetes

Objective:To investigate the relation between thyroid hormone and diabetic microvascular complications（DMVC）in euthyroid patients with type 2 diabetes（T2DM）.Methods:A retrospective analysis was performed for 785 patients with T2DM who were hospitalized in the Department of Endocrinology of Qinhuangdao First Hospital from June 2019 to August 2020.Therein 387 patients（49.30%）did not have diabetic microvascular complications,and 395 patients（50.70%）had at least one diabetic microvascular complication,and the prevalence of diabetic retinopathy（DR）was 15.16%（n=119）,the prevalence of diabetic nephropathy（DKD）was 31.08%（n=244）,and the prevalence of diabetic peripheral neuropathy（DPN）was 29.30%（n=230）,there were 68 cases（8.66%）with DR and DKD,70 cases（8.91%）with DR and DPN,98 cases（12.48%）with both DKD and DPN,and 45 cases（5.73%）with DR,DKD and DPN at the same time.Ask and record the gender,age,and course of diabetes in the included study population,measure height,weight,blood pressure,and detect fasting blood glucose（FPG）,fasting C peptide,glycated hemoglobin（HbA1c）,free triiodothyronine（FT3）,thyroxine（FT4）,thyroid stimulating hormone（TSH）,uric acid（UA）,blood lipids,cystatin-C（Cys-C）,homocysteine（Hcy）,e-Glomerular filtration rate（e GFR）,CKD-EPI method),urine microalbumin creatinine ratio（ACR）,BMI,etc.The median as the tangent point,FT3 was divided into A_FT3 group（1.58-2.69 pg/ml）and B_FT3 group（2.70-3.91pg/ml）,and FT4 was divided into A_FT4 group（0.70-0.98 ng/dl）and B_FT4 group（0.99-1.48 ng/dl）.TSH was divided into A_TSH group（0.35-2.50 u IU/ml）and B_TSH group（2.51-4.94 u IU/ml）with 2.5 u IU/ml as the cutpoint.20μmol/L was used as the cut-point for the diagnosis of hyperhomocysteinemia.To explore the relation between FT3,FT4 and TSH and microvascular complications.Results:1.The FT3 concentration was significantly lower than that in the group without microvascular complications in at least one microvascular complication group（t=4.501,P<0.05）.The FT3 concentration in the DR group was significantly lower than that in the DR-free group,the FT3 concentration in the DKD group was significantly lower than that in the DKD-free group,and the FT3 concentration in the DPN group was significantly lower than that in the DPN-free group（all P<0.05）.The FT4 concentration in the DKD group was significantly lower than that in the DKD-free group（P<0.05）,and there were no significant differences between DR and FT4 concentrations and between DPN and FT4 concentrations.There were no significant differences between DR,DKD,DPN and TSH concentrations.2.The prevalence of DR,DKD and DPN in A_FT3 and B_FT3 groups was 19.6%VS 10.8%,35.8%VS 26.4%,32.7%VS 25.7%,respectively,and the differences were statistically significant（P<0.05）.The prevalence of DR,DKD and DPN in the A_FT4 and B_FT4 groups was 16.1%VS 14.3%,28.5%VS 33.6%,28.2%VS 30.1%,respectively,and the differences were not statistically significant（P>0.05）.The prevalence of DR,DKD and DPN in the A_TSH group and the B_TSH group was 14.4%VS 17.5%,30.1%VS 34.0%,30.5%VS 25.3%,respectively,and the differences were not statistically significant（P>0.05）.3.The prevalence of high homocysteinemia in the A_FT3 group and B_FT3 group was 25%and 13.4%,respectively,with a statistically significant difference（P<0.05）.4.Logistic regression analysis showed that after adjusting for traditional risk factors such as age,diabetes course and BMI,FT3 was an independent risk factor for DR and DKD（OR=0.555,95%CI:0.364-0.846;OR=0.717,95%CI:0.524-0.981）,but not an independent risk factor for DPN.FT4 and TSH is not independent risk factors for DR,DKD,and DPN.Homocysteine was an independent risk factor for DKD（OR=1.752,95%CI:1.187-2.586）,rather than DR and DPN.5.The incidence of low FT3 in the HbA1c≥6.5%group and the HbA1c<6.5%group was 89.6%and 10.4%,respectively,with a statistically significant difference（P<0.05）.Conclusion:FT3 concentration is lower in euthyroid patients with type 2 diabetes and diabetic retinopathy and/or diabetic nephropathy,and patients with poor glycosylated hemoglobin control have a higher detection rate of low FT3,while no association between FT4 and TSH and diabetic microvascular complications was found.There may be an association between poor glycemic control,low FT3concentration,and microvascular complications in patients with T2DM,and future studies need to confirm the causal relationship and exact mechanism.