Effects of radioiodine therapy on fertility indicators among men with differentiated thyroid cancer: A cohort study

BACKGROUND: Following thyroidectomy, radioiodine therapy is the standard management of differentiated thyroid cancer. The effects of such treatment on testicular function remained a concern for cases and clinicians. OBJECTIVE: We aimed to observe changes in fertility indicators in men treated with ablation. MATERIALS AND METHODS: In this prospective cohort study, 18 men with differentiated thyroid cancer from June to December 2020 underwent thyroidectomy plus radioiodine therapy. Participants were grouped based on iodine dose (8 men with 30 mCi vs. 10 men with [Formula: see text] 150 mCi). Baseline values (V [Formula: see text] ) of the follicular stimulating hormone, luteinizing hormone, testosterone, and sperm analyses were measured 3 wk before iodine ablation and repeated 3 (V [Formula: see text] ) and 12 (V [Formula: see text] ) months later. They were analyzed once as a whole and once based on their groups via ANOVA and Friedman's tests where appropriate. RESULTS: The mean age of participants was 35.61 [Formula: see text] 9.74 yr. Follicular stimulating hormone levels showed a significant trend among all participants (V [Formula: see text] : 12.51 [Formula: see text] 1.72, V [Formula: see text] : 13.54 [Formula: see text] 1.41, and V [Formula: see text] : 13.10 [Formula: see text] 1.67 IU/mL; p [Formula: see text] 0.001). Luteinizing hormone showed a similar pattern (V [Formula: see text] : 4.98 [Formula: see text] 1.27, V [Formula: see text] : 5.65 [Formula: see text] 1.29, and V [Formula: see text] : 5.21 [Formula: see text] 0.95 IU/mL; p [Formula: see text] 0.001). Testosterone levels did not differ significantly from baseline. Sperm count decreased at the first checkpoint and returned to normal after 12 months (V [Formula: see text] : 38.22 [Formula: see text] 19.40, V [Formula: see text] : 32.05 [Formula: see text] 17.96, and V [Formula: see text] : 36.66 [Formula: see text] 18.81 million/mL; p [Formula: see text] 0.001). Sperm motility and morphology did not change significantly. CONCLUSION: Our research showed that even less than 5 GBq irradiation could induce a transient testicular dysfunction in the first 3 months of therapy, but it was mostly reversible after 12 months.