The Relationship Between Thyroid Dysfunction And Gestational Diabetes Mellitus In Pregnant Women

Objective: 1. To investigate the relationship between thyroid dysfunction during early pregnancy and gestational diabetes mellitus(GDM). 2. To explore the impact of thyroid dysfunction combined with GDM to pregnancy outcomes.Methods: 1. In accordance with the inclusion and exclusion criteria, a total of 9705 subjects were recruited and the blood was successfully collected from them. They are grouped according to the levels of TSH, FT4 and TPOAb, which include clinical hypothyroidism, subclinical hypothyroidism, clinical hyperthyroidism, subclinical hyperthyroidism, hypothyroxinemia, isolated positive thyroid autoantibody. A standard oral glucose tolerance test(OGTT) protocol was used to diagnose GDM, and the 3 glucose values were collected. Statistical analysis was performed to explore whether there are linear relationships between thyroid hormones and glucose values. Moreover, logistic regression analysis was applied to determine which thyroid disease will increase risk for GDM. 2. The method of recruiting subjects was same with the first part. Zero inflated Poisson regression and logistic regression models were incorporated to examine the associations of thyroid dysfunction combined with GDM to pregnancy outcomes which include macrosomia, fetal distress, hypertensive disorders complicatingpregnancy, amniotic fluid pollution, premature rupture of membrane and preterm birth.Results: 1. Three glucose values of the hypothyroxinemia group are higher than euthyroid subjects(t=-4.54, P﹤0.001; t=-6.96, P﹤0.001; t=-5.82, P﹤0.001); 2. The incidence rate of GDM is higher than euthyroid subjects only in hypothyroxinemia group(χ2=32.10, P ﹤ 0.001) among all of the thyroid dysfunction groups; 3. Multiple linear regressions were showed that there are negative correlations between FT4 and 3 glucose values; 4. After adjusted for maternal age and BMI, hypothyroxinemia was still associated with an increased risk for GDM(OR 1.49, 95%CI 1.19-1.87); The predicted percent of gestational diabetes decreased from 26.48% to 0.71% as FT4 increased from 1 to 45 pmol/L(P=0.002); 5. The incidence of macrosomia is more prevalent in subjects with isolated positive thyroid autoantibody and GDM(t=2.29, P=0.022); 6. Low FT4 levels combined with GDM and isolated positive thyroid autoantibody combined with GDM were positively correlated with preterm birth(t=3.26, P=0.001; t=2.66, P=0.008); 7. The combination of isolated positive thyroid autoantibody and GDM was associated with a 2.09-fold increased risk for premature rupture of membrane(OR 2.09, 95%CI 1.19-3.67).Conclusion: 1. Hypothyroxinemia in early pregnancy increased the risk of GDM and FT4 is a protective factor of GDM. 2. The incidence of macrosomia is more prevalent in subjects with isolated positive thyroid autoantibody and GDM;3. Low FT4 levels combined with GDM and isolated positive thyroid autoantibody combined with GDM were positively correlated with preterm birth; 4. The combination of isolated positive thyroid autoantibody and GDM increased the risk of premature rupture of membrane by 1.09-fold.