The Impact of Moderately High Preconception Thyrotropin Levels on Ovarian Reserve Among Euthyroid Infertile Women Undergoing Assisted Reproductive Technology

Background: Thyroid dysfunction is prevalent in reproductive-age women and has been identified as a risk factor for female infertility. However, it remains largely unclear whether subtle thyroid dysfunction, as estimated by moderately high thyrotropin (TSH) levels within the normal range, is associated with ovarian reserve in infertile women before assisted reproductive technology (ART) treatment. Methods: This cross-sectional study involved 3501 euthyroid infertile women, including 2189 women with TSH levels ≤2.5 μIU/mL and 1312 women with high-normal TSH levels (2.51–4.20 μIU/mL). Ovarian reserve markers were compared between women with low- and high-normal TSH levels. Correlation analysis and regression models were used to estimate the association of TSH levels with ovarian reserve. In addition, the association of subtle thyroid dysfunction with ovarian reserve was further evaluated after stratification for different infertility diagnoses and statuses of thyroid autoimmunity (TAI). Results: In the total population, women with high-normal TSH levels had significantly decreased anti-Müllerian hormone (AMH) concentrations ( p