In women of reproductive age who have thyroid cancer, their remaining egg supply is affected by radioactive iodine treatment, potentially reducing their fertility. These findings were presented at ENDO 2016, the 98th Annual Meeting of the Endocrine Society.1
“This is the first study ever to prospectively address the impact of radioactive iodine treatment on ovarian reserve. In our day and age, when growing numbers of women of reproductive age are diagnosed with thyroid cancer and when fertility problems are rampant, these findings should serve as an additional consideration for physicians contemplating radioactive iodine for their patients,” said Karen Tordjman, MD, associate professor of medicine at the Sackler Faculty of Medicine of Tel Aviv University in Israel, and senior author of the study. “Low-risk thyroid cancer patients may not derive any survival advantage from the treatment but may end up paying the cost of decreased fertility.”
“Earlier menopause has been reported in women undergoing radioactive iodine treatment, and given the finite number of primordial follicles women start with at birth, radiation injury to germinal cells is not expected to be reversible,” she cautioned.
The research team studied the effect of radioactive iodine treatment on the ovarian reserve of women treated for differentiated thyroid cancer (DTC) by measuring their blood levels of anti-Müllerian hormone (AMH) and following the patients for up to 1 year after treatment. A higher AMH level indicates that more eggs are remaining.
The study enrolled 30 premenopausal women age 20 to 45 years who were scheduled for treatment with radioactive iodine after their DTC surgery, plus an additional 5 women treated with radioactive iodine for Graves disease. All the women had reported regular menses prior to treatment, and 19 of them had children. Blood levels of AMH were measured at baseline and every three months for up to a year after treatment.
High radioactive iodine doses appeared to impair ovarian reserve. AMH levels decreased 45% at 3 months after treatment, and recovery was not complete after 1 year. Most women in this study received high doses, therefore the researchers could not determine if the dosage affected the ovarian reserve.
To examine a potential dose effect, 4 patients who had received low RAI doses for DTC were grouped with the 5 who had received low RAI doses for Graves disease. Among these 9 women, baseline AMH levels were low and remained low in later assessments.
The researchers noted that doses up to 30mCi, such as those given for ablation of thyroid remnant for hyperthyroidism, appear to be innocuous. The authors stated that this adds weight to the precautions currently advocated regarding radioiodine therapy in low-risk patients with differentiated thyroid cancer.
1. Yaish I, Azem F, Serebro M, et al. High dose radioiodine therapy affects ovarian reserve in women with differentiated thyroid cancer. Oral presentation at: ENDO 2016; April 1-4, 2016; Boston, Massachusetts. Abstract OR22-6.