Background

Although international guidelines have become more conservative on the use of radioactive iodine (RAI), it is still a cornerstone of the treatment of 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 function is important. Earlier studies evaluating Anti-Müllerian hormone (AMH) as a representative of ovarian reserve were either cross-sectional, had relative low numbers, had no patients with multiple RAI therapies, or had a relative 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. Before initial therapy and regularly thereafter, serum AMH was measured. Repeated measurement analysis was used to assess the changes of AMH concentrations, 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 five measurements, median follow-up 34 months). AMH concentrations changed non-linear 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.

Conclusion

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 remained stable. In patients receiving multiple RAI therapies, a further decrease was seen. Age at baseline significantly influenced AMH change over time. Herewith our results support a less aggressive treatment with RAI in low risk patients, especially in females over 35 years of age.