Thyroid Research Thyroid Research Archive Thyroid Cancer

Radioiodine therapy does not impair fertility in men with thyroid carcinoma

(November 2002)

The background of the study. Some men with thyroid carcinoma have transient decreases in sperm counts after radioiodine (I-131) therapy, but the effect of treatment on long-term fertility is not known. In this study, the fertility of men with papillary or follicular thyroid carcinoma treated with varying doses of radioiodine was determined.

How the study was done. The study subjects were 122 men with thyroid carcinoma who were less than 40 years old when treated between 1949 and 1997; older men were not studied because most had completed their families. All the men were treated surgically; 78 men then received 81 mCi (3 GBq) of radioiodine to destroy remaining normal thyroid tissue, and 44 men received 230 to 1280 mCi (8.5 to 47.3 GBq) I-131 to treat persistent or recurrent cancer. The men were asked at follow-up visits or by mail questionnaire if they had all the children they wished to have, and if they had not had children, whether this was by choice.

The results of the study. Among the 122 men, 29 had died or were lost to follow-up (median follow-up, 21 years. Among the remaining 93 men, 34 (37 percent) had not wished to have children. The remaining 59 men (63 percent) had fathered 106 children 3.5 to 18 years after radioiodine therapy. Twelve men who received a single 81 mCi (3 GBq) dose of radioiodine had fathered 20 children, 19 men who received >81 to <380 mCi (3 to 14 GBq) had fathered 36 children, and 28 men who received 380 to 1190 mCi (14 to 44 GBq) had fathered 50 children. None of the children had any major malformation.

The conclusions of the study. Radioiodine therapy does not reduce fertility in men with thyroid carcinoma.

The original article. Hyer S, Vini L, O'Connell M, Pratt B, Harmer C. Testicular dose and fertility in men following I¹³¹therapy for thyroid cancer. Clin Endocrinol 2002;56:755-8.