March 02, 2018
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Radioactive iodine treatment for thyroid cancer may adversely affect ovarian reserve

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Women with differentiated thyroid cancer treated with radioactive iodine ablation experienced decreased anti-Müllerian hormone levels 3 months after treatment with only partial recovery at 1 year after treatment, which may suggest an adverse effect of radioactive iodine in women of reproductive age, according to study findings.

“Many of the subjects treated for differentiated thyroid cancer are women in their reproductive years, often before having given birth for the first time,” Karen M. Tordjman, MD, director of the endocrine clinics at the Institute of Endocrinology at the Tel Aviv Sourasky Medical Center in Israel, told Endocrine Today. “The findings of this study suggest that radioiodine, given as part of the initial treatment for this cancer, could have a negative impact on the future reproductive potential of some of these women. The concerns raised by this study support the current approach that radioactive iodine ablative treatment be reserved to subjects in whom it offers a clear survival or disease-free advantage.”

Tordjman and colleagues evaluated data on 24 women (mean age, 34.3 years) with differentiated thyroid cancer who underwent radioactive iodine (RAI) ablation to determine the effect of RAI treatment on ovarian reserve by measuring the concentration of anti-Müllerian hormone (AMH) 1 year after treatment. A subgroup of five women (mean age, 33.6 years) who underwent RAI ablation for Graves’ disease were also evaluated. AMH levels were measured at baseline and 3, 6 and 12 months after RAI. Baseline AMH levels were 3.2 ng/mL in the differentiated thyroid cancer group and 2.6 ng/mL in the Graves’ disease subgroup.

In participants with differentiated thyroid cancer, baseline AMH level decreased by 49% at 3 months after RAI treatment from 3.25 ng/mL to 1.9 ng/mL (P = .001). In the entire cohort, some recovery in AMH levels was observed, but plateaued at 9 months; at 1-year, AMH concentrations were 32% lower compared with baseline (P = .016).

When the median age of 35 years was used as a cutoff, participants aged at least 35 years were more likely to experience a reduction in AMH at 3 months compared with younger participants (P = .007).

In participants with Graves’ disease, RAI ablation had no treatment effect on AMH levels.

Amenorrhea lasting up to 4 months was reported by two participants, and three reported irregular periods for at least 1 year after treatment. Menstrual irregularities were reported by 19.2% of participants with differentiated thyroid cancer.

“As this is a pilot study that followed a limited number of subjects for only a year, a larger and more prolonged prospective study is needed to confirm these preliminary data, and using fertility outcomes as hard endpoints, to determine if this effect on anti-Müllerian hormone translates into decreased fertility,” Tordjman said. “In the meantime, the authors suggest that serum levels of anti-Müllerian hormone could serve as an ancillary tool when planning radioiodine ablative therapy for women over the age of 35 who desire pregnancy.” – by Amber Cox

For more information:

Karen M. Tordjman, MD, can be reached at karent@tlvmc.gov.il.

Disclosures: The authors report no relevant financial disclosures.