Effect Of Assisted Reproductive Technology On Thyroid Function In Infertile Women

Objective: The thyroid gland is an important endocrine organ in the body and its functional status can have a direct impact on female reproductive activity.The prevalence of thyroid disorders is high among infertile women.With the encouragement of the "three-child policy" and the maturation of assisted reproductive technology(ART),more and more infertile women are undergoing ART.The most important step in ART treatment is controlled ovulation(COH),which has been shown to have an effect on thyroid function in IVF patients.However,the effect of COH on the thyroid axis in patients with subclinical hypothyroidism(SCH)has been less studied.In this study,we analyzed thyroid function before and after COH stimulation in infertile women with normal thyroid function and SCH who had been treated with levothyroxine(LT4)to understand the effect of ART on thyroid function and to provide a basis for early screening and diagnosis of thyroid function abnormalities in ART-treated infertile women.Methods: A total of 79 infertile women who underwent assisted reproduction at Northwest Women’s and Children’s Hospital from January 2020 to January 2022 and were followed up with thyroid function monitoring at the endocrinology clinic of Xi’an Central Hospital were collected.Among them,22 women with normal thyroid function with basal serum TSH <2.5u IU/ml;57 patients with subclinical hypothyroidism were given at least 25ug/day of oral levothyroxine(LT4)before initiating assisted reproduction,with a therapeutic control target of 0.27 u IU/ml <TSH <4.2u IU/ml.The data were collected on the patients’ age,assisted reproduction protocol,and thyroid function parameters.SPSS 25.0 software was used for data analysis.Data satisfying normal distribution were expressed as mean ± standard deviation,and measurement data not obeying normal distribution were described by median and interquartile spacing;count data were described using frequency,and measurement data satisfying normal distribution were selected by paired t-test or independent sample t-test The paired non-parametric Wilcoxon rank sum test or independent sample non-parametric Wilcoxon rank sum test was used for non-continuous data or non-normally distributed data,and the chi-square test or Fisher’s exact probability method was used for comparison between groups of count data.Test level: α=0.05,and P<0.05 was considered statistically significant.Results1.No statistically significant differences were seen in age,ART protocol,or transplantation method between the two groups(p=0.08 > 0.05;p=0.49 > 0.05;p=0.92 >0.05).2.In fresh embryo transfer,there was no significant difference in clinical pregnancy rate between basal serum TSH ≤ 2.5u IU/ml and 0.27 < TSH < 4.2u IU/ml(p=0.98 >0.05).3.After COH stimulation,TSH levels increased in both groups compared with the basal TSH levels before COH stimulation,and the increase was statistically different(p=0.01<0.05;p=0.01<0.05);LT4 dose increased in both groups compared with the previous one,and it was statistically significant(p=0.01<0.05;p=0.01<0.05);in the subclinical hypothyroidism group FT3 and FT4 were decreased than before with statistical significance(p=0.02 < 0.05;p=0.01 < 0.05);in the normal nail function control group,serum FT3 and FT4 levels were also decreased than before,and the decrease of FT4 level was statistically significant(p=0.06 > 0.05;p=0.02 < 0.05).Conclusion:1.Women on ART have significantly elevated serum TSH levels during COH,and the vast majority require increased doses of LT4.2.COH has a large effect on women with subclinical hypothyroidism who have been treated with levothyroxine.3.There was no significant difference in the fresh transplant clinical pregnancy rate between the normal thyroid group and the subclinical hypothyroid group that had been treated with levothyroxine(LT4).