Background: Although international guidelines have become more conservative on the use of radioactive iodine (RAI) therapy, it is still one of the cornerstones of the treatment of patients with advanced differentiated thyroid cancer (DTC). As a large proportion of females diagnosed with DTC is in their reproductive years, knowledge about the effect of RAI on their gonadal and reproductive function is important. Earlier studies evaluating Anti-Müllerian hormone (AMH) as a representative of ovarian reserve were either cross-sectional, had relatively low numbers, had no patients with multiple RAI therapies, or had a relatively short follow-up. The primary aim of our study was, therefore, to prospectively evaluate the effect of RAI on AMH in women undergoing treatment for DTC. Methods: We included females, aged 16 years until menopause, who were scheduled to undergo their first RAI treatment for DTC at our hospital. Serum AMH was measured before initial therapy and regularly thereafter. Repeated measurement analysis was used to assess the changes of AMH concentrations over time, and how this is influenced by age and cumulative RAI dose. Results: Longitudinal AMH assessments were available in 65 patients (mean age 32 years, median of five measurements during median follow-up of 34 months). AMH concentrations changed nonlinear over time, decreased until 12 months in the single RAI group (-55%), and stabilized thereafter. In the multiple RAI group, after stabilization, a further decrease occurred (-85% after 48 months). Age in both RAI groups significantly influenced AMH change over time, with younger patients (<35 years of age) showing a less steep decrease. Conclusions: In a population of female DTC patients treated with total thyroidectomy and a single RAI therapy, AMH concentrations significantly dropped during the first year after initial therapy, and thereafter they remained stable. In patients receiving multiple RAI therapies, a further decrease was seen. Age at baseline significantly influenced AMH change over time. These results support a less aggressive treatment with RAI in low-risk patients as is advocated in the current American Thyroid Association (ATA) guidelines, especially in females older than 35 years of age with the desire to have a child.
Keywords: AMH; differentiated thyroid cancer; longitudinal analysis; ovarian reserve; radioactive iodine.