Infertility Risk After Radioactive I-131 Treatment

Effects of I-131 on Reproductive Function

Spermatogonia are highly sensitive to radiation, with doses as low as 0.1 Gy leading to short-term cessation of spermatogenesis, affecting male fertility 1
Doses of 2-3 Gy affect spermatogonial stem cells and cause long-term azoospermia in males 1
Radioactive iodine (I-131) is classified as having "intermediate risk" for female fertility, with studies showing a decline in anti-Müllerian hormone (AMH) levels after treatment, according to the American Society of Clinical Oncology 2, 3
RT-related ovarian follicle loss already occurs at doses of <2 Gy, impacting female fertility 1
The effective sterilizing dose decreases with increasing age, ranging from 16 Gy at 20 years to 14 Gy at 30 years, in females 1

A dose of 3.7 GBq (100 mCi) of I-131 is commonly used for thyroid cancer treatment following thyroidectomy, with doses ranging from 3.7-7.4 GBq (100-200 mCi) for patients with distant metastases from differentiated thyroid cancer, as recommended by the American Thyroid Association 4
For neuroendocrine tumors, I-131-mIBG activities typically range between 7.4 and 11.2 GBq administered at 3-6 month intervals, according to the European Neuroendocrine Tumor Society 5, 6

Based on radiation dose-response relationships, a single 3.7 GBq dose would be expected to cause temporary effects on fertility in some patients, but permanent infertility would be uncommon, with a strength of evidence level of moderate 1
All cancer patients of reproductive age should receive complete oncofertility counseling as early as possible in the treatment planning process, as recommended by the American Society of Clinical Oncology 1
Sperm cryopreservation before initiation of I-131 treatment is standard of care and should be discussed with male cancer patients, according to the American Urological Association 1
For female patients, options may include oocyte or embryo cryopreservation, ovarian tissue cryopreservation, or ovarian transposition depending on individual circumstances, as recommended by the American Society for Reproductive Medicine 7
Gonadal shielding during treatment may help reduce radiation exposure to reproductive organs, with a strength of evidence level of low 7