Thyroid Function During Early Pregnancy Associated With The Risk Of Gestational Diabetes Mellitus

ObjectiveTo explore the relationship between thyroid function during early pregnancy and gestational diabetes mellitus（GDM）,and the possible predictive value of thyroid function for GDM.MethodsFrom January 2017 to February 2018,a total of 1,429 pregnant women were enrolled as subjects of this study.Thyroid function（TSH,FT₃,FT₄,TPOAb）and fasting plasma glucose（FPG）were detected during early pregnancy,and the general information of pregnant women,such as age,height,weight,blood pressure and gravidity and parity were collected,followed up to 75g oral glucose tolerance test（OGTT）at 24～28 weeks of gestation.According to the diagnostic criteria of GDM,they were divided into the GDM group and the normal glucose tolerance（NGT）group.The correlation between thyroid function level in early pregnancy and the occurrence of GDM was analyzed statistically and the diagnostic value of GDM was predicted by using the receiver operating characteristic（ROC）curve analysis.Results1.The age,BMI,gravidity,parity and the fasting plasma glucose in early pregnancy of pregnant women in GDM group were significantly higher than that in NGT group（P<0.05）.There were no significant difference in systolic and diastolic blood pressure（P>0.05）.2.The morbidity of hypothyroxinemia during early pregnancy in GDM group was significantly higher than that in NGT group（P<0.05）.There were no statistically significant difference in the morbidity of overt hypothyroidism,subclinical hypothyroidism,overtl hyperthyroidism,subclinical hyperthyroidism,isolated TPOAb positive and in the rate of normal thyroid function（all P>0.05）.3.The FT₄ during early pregnancy in GDM group was significantly lower than that inNGT group,and the FT₃/FT₄ ratio in GDM group was significantly higher than thatin NGT group（both P<0.05）.There were no significant difference in TSH,FT₃ andTPOAb between the two groups（P>0.05）.4.The ratio of FT₃/FT₄ in early pregnancy were positively correlated with earlypregnancy FPG,OGTT-0,OGTT-1 and OGTT-2（r=0.145,0.183,0.179,0.156,allP<0.01）,and FT₄ is negatively correlated with OGTT-2（r=-0.060,P<0.05）.TPOAb in early pregnancy was positively correlated with TSH,FT₃/FT₄（r=0.086,0.065,both P<0.05）.5.The incidence of GDM was positively correlated with age,BMI,gravidity and parity（r=0.198,0.193,0.139,0.086,all P<0.01）.Multiple regression analysis showed that FT₃/FT₄,early pregnancy FPG,age,and BMI were independent risk factors for GDM.6.The FT₃/FT₄ ratio of the study subjects was analyzed by ROC curve,which showed that the area under ROC curve was 0.625（95%CI 0.582-0.667,P<0.0001）,the best diagnostic boundary value of FT₃/FT₄ level in early pregnancy was 0.3036,the sensitivity of this cut point was 65.83%and the specificity was 56.01%.To select different boundary values,the sensitivity and specificity of different GDM screening will be obtained.As the FT₃/FT₄ ratio gradually increases,the sensitivity of GDM screening gradually decreases and the specificity gradually increases.ConclusionsThe higher the FT₃/FT₄ ratio during early pregnancy,the higher the risk of GDM.And the best diagnostic threshold for predicting GDM was 0.3036.With the gradual increase of FT₃/FT₄ ratio,the sensitivity of GDM screening gradually decreased and the specificity gradually increased.