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Altered thyroid hormone level in offspring exposure to high estrogen level during the first trimester of pregnancy

      Objective

      To investigate whether the maternal high E2 environment in the first trimester increases the risk of thyroid dysfunction in children born after in vitro fertilization.

      Design

      Observe the thyroid function of children born after in vitro fertilization, measure the level of serum FT3, FT4, T3, T4, and TSH, and investigate whether the maternal high E2 level has correlation with thyroid hormones of children born after in Vitro Fertilization.

      Materials and Methods

      Total 415 singletons born after fresh embryo transfer (ET) (n =140), frozen ET (FET) (n = 171) and natural conception (NC) (n = 104), aged 3–10yr, were studied, IVF children were conceived after traditional IVF. All children were thoroughly examined, and serum FT3, FT4, T3, T4,and TSH were measured, maternal serum E2 levels during the first trimester of pregnancy were also investigated.

      Results

      The mean serum E2 levels of women undergoing fresh ET at 4 and 8 weeks of gestation were significantly higher than those of the women undergoing frozen ET and the women with NC (P <0.01). Serum E2 levels of women undergoing fresh ET at 4 and 8 weeks of gestation were positively correlated to those on the hCG administration day (r = 0.5 and r = 0.4, P < 0.01). The levels of T4, FT4 and TSH after fresh ET were significantly higher than that after frozen ET and NC (P <0.01), whereas no significant differences in the concentrations of FT3 or T3 were observed. Furthermore, maternal serum E2 level on the hCG administration day positively correlated with T4 and FT4 in IVF-children (r=0.33, P<0.01 and r=0.23, P < 0.05, n=118). Further studies are needed to confirm these findings and to better determine their etiopathogenesis and clinical significance.
      Tabled 1Comparison of T3, FT3, T4 , FT4 and TSH levels among IVF-ET, IVF-FET children and natural conception.
      NC (n=104)IVF-FET (n=171)IVF-ET (n=140)
      T3 (nmol/L)2.28 ±0.382.32 ±0.442.36± 0.29
      FT3(pmol/L)5.87 ±0.696.02 ±1.016.11±0.65
      T4(nmol/L)102.82±16.01101.03±15.50108.21 ±16.59 *,##
      FT4(pmol/L)16.12±2.1316.51±1.1316.86 ±1.64**
      TSH (mIU/L)2.43±1.122.42±1.022.71 ±1.24* ,#
      **P<0.01 or *P<0.05 vs NC;##P<0.01 or #P<0.05 vs IVF-FET

      Conclusion

      The maternal high E2 environment in the first trimester is correlated with increased risk of thyroid dysfunction. Evaluation of serum E2 before ET should be adopted to reduce the possibility of high E2 exposure to gamete/embryo.