Comprehensive review of international guidelines on subclinical hypothyroidism and thyroid autoimmunity in infertile women

Thyroid disorders, particularly subclinical hypothyroidism (SCH) and thyroid autoimmunity (TAI), are prevalent among infertile women and may adversely influence assisted reproductive technology outcomes. Multiple international societies have published clinical guidelines addressing these conditions; however, important discrepancies persist regarding screening strategies, thyroid-stimulating hormone (TSH) thresholds, and treatment indications. This review compares recent recommendations from the Korean Thyroid Association (KTA 2023), the American Society for Reproductive Medicine (ASRM 2024), the European Thyroid Association (ETA 2021), and the European Society of Human Reproduction and Embryology (ESHRE 2023). Similarities include targeted screening in high-risk populations and levothyroxine treatment for overt hypothyroidism and selected high-risk SCH cases, whereas key differences relate to TSH cutoff values and the management of SCH in the presence of TAI. Recognition of these inter-guideline differences is necessary to support the development of standards tailored to specific countries, healthcare systems, or institutional practices.