Counseling Female Thyroid Cancer Patients on Radioactive Iodine and Fertility

In this issue of Thyroid, Drs. Anagnostis and Bosbou raise important points around the fertility concerns of radioactive iodine (RAI) use in females with differentiated thyroid cancer (DTC). ¹ The 2025 ATA DTC management guidelines include a “Good Practice Statement” (43D) that female patients receiving RAI should be counseled that such therapy has not been shown to impact future fertility. ² Women of reproductive age, particularly if pregnancy is desired in the near future, often ask about the optimal timing recommended for the initial therapy of DTC, which may include postoperative RAI ablation in select intermediate- and high-risk cases. Although there are some data suggesting that a delay (defined as >3 months after total thyroidectomy) of RAI ablation may result in an incomplete response to DTC treatment, the majority of the current literature affirms that such delays do not affect overall survival, likely due in part to the overall insidious nature of most DTCs. This is reassuring, but the question of possible harm resulting from any RAI use remains a frequent consideration in the clinical setting. In women of reproductive age, these discussions of harms also often extend to the potential adverse effects of RAI on future fertility.

This topic is complicated by the heterogeneity in the definition of future fertility, as outlined by the authors. The available literature reports the associations between administration of RAI and outcomes that include trends of serum anti-Müllerian hormone (AMH) concentrations, as well as objective clinical measures, such as the absence or presence of menstrual irregularities, miscarriage rates, clinical pregnancy rates, and onset of menopause. Although lower serum AMH levels may be reflective of decreased ovarian reserve, at least for the short term, following RAI administration, clinical pregnancy rates have not been shown to be significantly different in the long term, even after accounting for potential confounders, in the vast majority of studies. ³ Importantly, permanent ovarian failure is extremely unlikely after RAI treatment. ⁴

Current understanding is limited by the availability of mostly retrospective cohort analyses and systematic reviews and meta-analyses on this topic. There is a need for further prospective cohort data that will provide further clarification, but in the current setting, it is reassuring that overall clinical pregnancy rates do not appear to be associated with RAI use for the treatment of DTC, consistent with our recommendations. Patient-centered counseling and shared decision-making around the potential risks of DTC therapy, including possible ovarian function risks associated with postoperative RAI ablation, particularly in women with a more limited reproductive lifespan, should be the cornerstone of preconception DTC management.