Radioactive iodine (131I) effects on male fertility

Radiometabolic therapy with radioactive iodine (I) is the standard treatment for differentiated thyroid cancer and is also currently the treatment of choice for Graves' disease in the United States. and in most countries. Men younger than 40 years of age represent about 10% of all radiometabolic treatments. Thus, the question arises whether I therapy is able to induce a damage to the fertility potential.

The different effects caused by I therapy employed in cancer and hyperthyroid patients are reviewed. Most articles about the first category of patients show a damage to the germinal epithelium directly related to the cumulative dose delivered. Although the small amounts used in hyperthyroidism are usually well tolerated in terms of sterility risk, the impairment caused by hyperthyroidism per se is probably higher than that caused by I treatment.

Young cancer patients, particularly those with node or lung metastases, who will probably undergo repeated treatments should be aware of the potential risks to their fertility. An evaluation of testicular function is thus advisable. When an impairment of fertility potential is already present, the option of freezing semen should be considered. The available studies concerning I therapy in hyperthyroidism suggest that this treatment does not cause a worsening of semen analysis but an amelioration in affected patients.