Trimester-and Method-specific Reference Intervals For Thyroid Tests In Pregnant Chinese Women Of Jinan

Objective:To establish the gestational month-specific stage (frist trimester of pregnancy T1, second trimester T2, the third trimester of pregnancy T3) reference intervals for triiodothyronine FT3thyroxine FT4thyrotropin TSH in women in the area of shandong. Pregnancy has a profound impact on the thyroid glandand thyroid function. When the mother in the frist trimester of pregnancy, the TBG levels in the serum will nearly doubled than ordinary, and continued until the end of the delivery. The change Include:The gland increases10%in sizeduring pregnancy in iodine-replete countries and by20%-40%in areas of iodine deficiency. And the production of thyroxine(T4) and triiodothyronine (T3) increases by50%, along with a50%increase in the daily iodine requirement. To meet the needs of the body during pregnancy。All These physiological changes may result in hypothyroidism in the later stages of pregnancy in iodine-deficient women who were euthyroid in the first trimester. The range of thyrotropin(TSH), under the impact of placental human chorionic gonadotropin (hCG), is decreased throughout pregnancy.Under the action of the high levels of estrogen and HCG, and promote the liver make more TBG. High TBG concentrations in serum samples tend to result in higher FT4values,whereas lowalbumin in serum likely will yield lower FT4values. The serum of pregnant women is characterized by higher concentrations of TBG and nonesterified fatty acids and by lower concentrations of albumin relative to the serum of nonpregnant women. When mother in16to20weeks of pregnancy, the TBG in serum nearly double above, until to the end of the delivery. Due to more than99%of all three iodine in serum glands original triiodothyronine (T3), thyroxine (T4) are combination with TBG. Therefore, in order to satisfy the maternal metabolism and fetal development need, mother must synthesize more T3and T4. In addition, in the early weeks of pregnancy, serum hCG levels increase, stimulates the thyrotropin increased, feedback inhibition TSH secretion, resulting in a low level of TSH in the first trimester of pregnancy. Therefore, to correctly judge the thyroid hormone levels of pregnant women during pregnancy, we need to establish a normal reference range of pregnancy-specific thyroid hormone.Methods:According to the United States national institute of clinical biochemical (NACB) guidelines. which recommend the establishment of TSH normal reference range, the object of study is the pregnancy women who take a regular examination during the pregnancy in Shandong provincial hospital in jinan region from May2012to March2013. Inclusion criteria:(1) without a family history of thyroid disease, past medical history or other autoimmune diseases history;(2) No history of administration of drugs can affect thyroid function (except estrogen);(3) no goiter;(4) anti-thyroid peroxidase antibody positive (TPOAb) are negative;(5) no hyperemesis gravidarum, preeclampsia, trophoblastic cell disease history;(6) single pregnancy;(7) No anti thyroglobulin。We carefully selected411women in pregnancy (4weeks to40weeks) after this guidelines, and collected120normal non-pregnancy with normal thyroid function cases who visits in Obstetrics and Gynecology, Shandong Provincial Hospital outpatient in the same period as a control group. More than531cases of the study group and control group patients were taken the TSH stratified analysis. The next day, after a medical examination,we take about5ml venous blood of the fasting people and then put the venou blood into a the procoagulant tube and placed in a-70°C refrigerator for centralized testing. Serum for the determination of thyroid stimulating hormone (TSH), free thyroxine (FT4), free three triiodothyronine (FT3), anti-thyroglobulin antibodies (TgAb), anti-thyroid peroxidase antibody (TPOAb), promote thyroid hormone receptor antibody (TRAb). Detection method for FT3, FT4, TSH, TPOAb TGAb, TRAb is electrochemiluminescence immunoassay,by the reagent of Roche Diagnostics Co., Ltd.(Roche, Cobas6000,-E601). The TSH direct use the electrochemical immunoassay luminescence method,sensitivity <0.001mIU/L.For TSH. FT3, FT4, TSH, TPOAb, TGAb, TRAb the batch coefficient of variation (CI) were lower than10%.Detect serum FT3, FT4, TSH level, divided into early pregnancy, mid-pregnancy, late pregnancy three groups, each group≥120. As each index from2.5to97.5percentage. On each group get all the data packets input EXCEL spreadsheet application SPSS17.0version used for statistical analysis. First of all, the general index age, gestational age normality test, normal distribution. Comparing the two single-factor analysis of variance (one-way ANOVA) to compare. FT3, FT4normal distribution, TSH was non-normal distribution. FT3, FT4, TSH each set of data using the median, said each selected95%confidence interval and the reference range, a minimum of P2.5P97.5capped. FT3, FT4, TSH between any two non-parametric tests that rank-sum test to compare P<0.05was considered statistically significant.Results:During pregnancy,the level of TSH is lowest in12week, then increased gradually and finally became stable during the third trimester of pregnancy(T3). During T1T2and T3, the median level of TSH is gradually increase and the median level of FT3and FT4is gradually decline. FT3levels of the frist trimester is lower than non-pregnancy levels, with the gestational age increasing, FT3levels showed a decrease trend. FT4levels of the frist trimester higher than non-pregnancy levels, after gradually decreased with increasing gestational age, second trimester and third trimester of pregnancy FT4levels below the level of non-pregnancy. TSH levels of the frist trimester of pregnancy is lower than non-pregnant, shorter duration, increased gradually after the second trimester and third trimester of pregnancy TSH levels TSH levels higher than non-pregnant. Conclusions:Pregnant women’s thyroid hormone changes because the endocrine change.The changes have greater differences with non-pregnancy period. The same time, race, living areas, ample iodine determination, indicator reagent method can significantly affect the normal reference range of pregnancy-specific thyroid function indicators, the study of pregnant women-specific reference range is difference of the reference range of the guidelines of thyroid function results in the American Thyroid Association (ATA) recommend, therefore, it is recommended that each laboratory in each region in accordance with the United States Institute of clinical Biochemistry (NACB) recommended screening method to determine the local normal pregnancy women-specific thyroid function reference range.Our study is conducive to the proper diagnosis the disorders of thyroid function during pregnancy,and conducive to the proper treatment of this disease.