A Preliminary Study On The Reference Range Of Thyroid Hormone In Early Pregnancy And Its Relationship With Gestational Diabetes Mellitus In Our Hospital

Part I A Preliminary Study on The Normal Reference Range of Thyroid Hormones in Early Pregnancy in Our HospitalObjective:To explore the normal reference range of thyrotropin（TSH）and free thyroid hormone（FT4）in early pregnant women in our hospital.Methods:The data of 801 pregnant women with local household registration or local residence permit with 6 weeks to 13 weeks of pregnancy,from October2016 to October 2018,were collected.The data of 621 healthy non-pregnant women who underwent pre-pregnancy examination in the same period were taken as control.The general clinical data of the patients were collected and the levels of thyrotropin（TSH）and free thyroid hormone（FT₄）were observed.All data were analyzed by SPSS 17.0 statistical software.Results:1.The median level of TSH in normal early pregnant women was significantly lower than that in non-pregnant women（1.07[0.06-3.95]uIU/ml vs1.62[0.45-4.70]uIU/ml）.The average rank of TSH study group and control group were 599.35 and 856.16,respectively,and the difference was statistically significant（P<0.01）.The median level of FT₄ in normal early pregnancy was the same as that in non-pregnant women（0.89[0.65-1.35]）vs（0.89[0.70-1.11]）.The average rank of FT₄ in the study group and the control group were 724.38 and694.88,respectively.P=0.179,the difference was not statistically significant.2.When analyzed by age groups（age<28 years,28 years≤age≤35 years old,and age>35 years old）,the average rank of TSH in non-pregnant women and pregnant women were（178.62 vs 119.77）,（430.51 vs 300.08）,and（244.59 vs 180.41）.The average rank of FT₄ in non-pregnant women and pregnant women were（144.66 vs178.24）,（327.33 vs 378.74）,and（175.22 vs 208.70）,respectively.Man-Whitney U test showed the difference was statistically significant（P<0.01）.3.The median of TSH and FT₄ were calculated according to the different gestational weeks in the first trimester of pregnancy.The median TSH from 6 weeks of gestation to 13weeks of gestation were 1.405 uIU/ml,1.080 uIU/ml,1.060 uIU/ml,1.185 uIU/ml,1.120 uIU/ml,0.990uIU/ml,1.150 uIU/ml,and 0.940 uIU/ml,respectively.The median FT₄ from 6 weeks of gestation to 13 weeks of gestation were 0.880 ng/dl,0.900 ng/dl,0.915 ng/dl,0.870 ng/dl,0.880 ng/dl,0.870 ng/dl,and 0.875 ng/dl,respectively.4.According to the stratification of gestational weeks:0 was non-pregnant women,1 was pregnant women of 6 to 7 weeks of gestation,and 2were pregnant women of 8 to 13 weeks of gestation.Kruskal Wallis test was used to compare the levels of FT4 and TSH among the three groups.The results showed that the average rank of TSH in the first trimester of pregnancy was 856.16 vs686.52 vs 591.26,and the average rank of FT₄ in the first trimester of pregnancy was 658.74 vs 702.71VS591.26,and 658.74 vs 591.26,respectively.By Kruskal Wallis test,the results showed that the values of TSH and FT4 in early pregnancy were 140.160 and 19.301 respectively,and the difference was statistically significant（P<0.01）,which suggested that there were differences in the overall distribution of FT₄ and TSH among the three groups.Conclusion:The normal reference range of TSH in early pregnancy in our hospital is 0.06 to 3.95 uIU/ml.The normal reference range of FT₄ in early pregnancy in our hospital is 0.65 to 1.35 ng/dl.TSH>3.95 uIU/ml is the diagnostic cutoff point for pregnant women with hypothyroidism.TSH levels are generally higher in the non-pregnant group than that in the pregnant group.The FT₄ level of pregnant women at 8 to 13 weeks of gestation is higher than that of non-pregnant women.Part II Study on The Relationship Between Thyroid Hormone in Early Pregnancy and Gestational Diabetes MellitusObjective: To observe the relationship between the level of thyroid hormone in early pregnancy and the level of OGTT detected at 24 to 28 weeks of gestation,for the purpose of investigating the relationship between early pregnancy TSH,FT4,and gestational diabetes mellitus（GDM）.Methods: 1.The dataof 718 pregnant women who were registered and underwent antenatal examinations in our hospital from October 2016 to October 2018 were collected for the study.The general data of patients and the results of TSH,FT4,renal function,blood lipid,fasting blood glucose,and oral glucose tolerance（OGTT）in our hospital at 24 to 28 weeks of gestation were collected.The subjects were excluded for having the history of thyroid disease and diabetes before pregnancy.2.According to the ninth edition of obstetrics and gynecology（GDM）diagnostic criteria of gestational diabetes mellitus,the subjects were divided into GDM group and non-GDM group.The GDM group was study group（n = 177）and the non-GDM is control group（n = 541）.All data were statistically analyzed by SPSS 17.0 statistical software.Results:1.The median of TSH of GDM group and non-GDM group in early pregnancy was 1.10 u IU/ml vs 1.08 u IU/ml.2.The median of FT4 of GDM group and non-GDM group in early pregnancy was 0.86 ng/dl vs 0.93 ng/dl.3.The average rank of TSH of GDM group and non-GDM group in early pregnancy was（364.93 vs 357.72）.The result of Mann-Whitney U test showed that there was no significant difference in TSH in early pregnancy between GDM group and non-GDM group（P=0.688）.4.The average rank of FT4 in early pregnancy was（300.90 vs 378.67）in GDM group and non-GDM group,and the difference was statistically significant（P < 0.010）.The FT4 level of pregnant women in non-GDM group was higher than that in GDM group.5.The correlation between age,fasting blood glucose in early pregnancy,FT4,and the incidence of GDM was analyzed by Logistic regression analysis.The results showed that FT4 was the protective factor of GDM（OR=0.140,95%CI=0.051-0.391）.Age and fasting blood glucose in early pregnancy were risk factors（OR=1.075,95%CI was 1.037-1.114）（OR=1.397,95%CI was 1.128-1.731）.Conclusion: There is no significant difference in TSH between GDM group and non-GDM group,and there is no correlation between TSH in early pregnancy and gestational diabetes mellitus.FT4 is the protective factor of gestational diabetes mellitus.The lower the FT4 is in the early pregnancy,the higher the incidence of gestational diabetes mellitus is.The higher the fasting blood glucose is in the early pregnancy andthe older the age is,and the higher the possibility of gestational diabetes mellitus in the middle and late pregnancy will be.