Investigating the relationship between in vitro embryo development and maternal hypothyroidism

Abstract

Background: Hypothyroidism decreases folliculogenesis, ovulation, endometrial thickness, and differentiation then impairs the physiological functions of the ovaries, uterus, cervix, and placenta, affecting pregnancy and birth. Therefore, we conducted this study, believing that investigating how hypothyroidism affects infertile women’s IVF treatment will positively impact treatment tactics and success. Aim: To determine serum TSH of infertile women and investigate whether it affects the quality of blastocysts. Materials and Methods: A total of 208 infertile women were included in the study, and the hormone thyrotropin (TSH) was determined. A case-control study design was performed following the recommendations of the International Thyroid Association. The determination of TSH hormone in serum was determined by the ELISA-Fluorescence method. Oocytes were classified according to their development and blastocysts into 5 grades: A, B, C, D, and E according to the Kato ladies’ clinical classification. The correlation of qualitative parameters was calculated by the chi-square test, the difference of numerical values was calculated by independent t-test, binary logistic regression analysis was used to calculate risk, and the probability of statistical truth was calculated as P<0.05. Results: In our study, we divided the data of 1171 oocytes from 333 cycles of 208 women aged 21-48 years into the control group (n=865) if the serum thyrotropin hormone level was within the recommended range (<2.5 mIU/L) and the case group (306) if it was >2.5 mIU/L. A statistically significant difference was found when comparing differences in oocyte development between groups (p<0.05), and serum thyrotropin levels higher than the recommended value were associated with a 1.5-fold increased risk of delayed oocyte development (OR=1.578 p<0.05). Based on the implantation rate, blastocysts of grades A, B, and C were classified as good-grade blastocysts, and grade D and E blastocysts were classified as poor-grade blastocysts. When considering whether the serum thyrotropin hormone was higher than the recommended level was a risk factor, the risk of poor-grade blastocysts was increased by 2.5 times (OR= 2.579 p<0.05). Conclusions: 1. Although there was a statistically significant relationship between the groups, the quality parameters of oocyte development did not appear to be a risk factor for the poor quality of oocyte development. 2. Our study revealed a statistically significant difference between groups, highlighting the significance of thyrotropin hormone levels in reproductive health. Specifically, we found that when thyrotropin hormone levels exceeded recommended values, the risk of developing poor-grade blastocysts increased by 2.5 times. This association is likely linked to the disruption of normal physiological functions in crucial reproductive organs, including the ovary, cervix, and placenta. Elevated thyrotropin levels appeared to negatively impact key reproductive processes, such as folliculogenesis, ovulation, and the thickness and differentiation of the endometrium. These findings underscore the importance of maintaining thyroid hormone balance in optimizing fertility and early embryo development. Further research and clinical monitoring are warranted to better understand and address the implications of thyroid function on reproductive outcomes.