Research Of The Association Between Thyroid Hormone Levels And Gestational Diabetes Mellitus During The Pregnancy

Objective:Through prospective cohort study,we can investigate the levels of thyroid hormones in pregnant women in Wuhan area,and explore the correlation between maternal thyroid hormone levels during pregnancy and gestational diabetes mellitus（GDM）.Subjects and Methods:The respondents were pregnant women who participated in the“Tongji Maternal and Child Health Cohort”（TMCHC）from January 2013 to May 2016 and were regularly followed up.In the early pregnancy,a questionnaire survey was conducted among pregnant women in the cohort to collect information on the basic conditions and lifestyle of pregnant women,such as age,height,pre-pregnancy weight,pregnancy history,last menstrual period,and so on.Pregnant women who were tested serum free triiodothyronine（FT₃）,free thyroxine（FT₄）,and thyroid stimulating hormone（TSH）within 20 weeks of pregnancy were included in the study.These pregnant women also completed oral glucose tolerance test within 24-28 weeks of pregnancy.According to the results of thyroid hormone determination,the thyroid hormone levels were grouped into the logistic regression model in the form of quartiles.The concentrations from low to high were Q1,Q2,Q3,and Q4.The odds ratio（OR）and the 95%confidence interval（CI）were calculated to analyze the association between thyroid hormone levels in pregnant women and the risk of developing GDM.Results:A total of 1171 pregnant women were included in the study.The average age of pregnant women was（27.94±3.41）years old,and the average body mass index（BMI）before pregnancy was（20.90±2.75）kg/m².The incidence of GDM was 7.7%.The average level of FT₃ was（3.03±0.50）pg/mL,the average level of FT₄ was（1.25±0.23）ng/dL,and the mean level of TSH was（1.69±1.28）uIU/mL.The average level of FT₃/FT₄ was（2.49±0.49）.The Logistic regression analysis showed a significant positive correlation between FT₃ and GDM.Taking Q1 group as reference,the OR（95%CI）value of Q4 to Q1 was 3.31（1.22-4.38）within 20 weeks of pregnancy,after adjusting for pregnant women’s age,pre-pregnancy body mass index,detection of gestational age,related hormones and other potential confounding factors,The positive correlation still exists.The OR（95%CI）value of Q4 to Q1 was2.14（1.06-4.30）within 20 weeks of pregnancy.Sensitivity analyses were performed after excluding the elderly,pre-pregnancy overweight and pregnant women with FT₃extreme values,and FT₃ was still positively correlated with GDM.However,TSH,FT₄,and FT₃/FT₄ had not been found to be significantly associated with GDM.Conclusion:Elevated levels of FT₃ suggested an increased risk of GDM,so detecting thyroid function-related hormones from pregnant women in early pregnancy is of great significance in preventing a series of adverse pregnancy outcomes in people at high risk of GDM.