Effects of radioiodine treatment for differentiated thyroid cancer on testis function

Summary Objective To evaluate the effects of radioactive iodine (RAI) treatment for differentiated thyroid cancer (DTC) on testis function. Design A prospective longitudinal single‐centre study was performed. A comprehensive andrological evaluation including hormonal assessment, semen analysis and scrotal ultrasound was undertaken in male patients undergoing RAI treatment for DTC. Methods Hormonal assessment of FSH, LH, testosterone (T), sperm concentration and motility and testis volume were determined in 20 patients in basal conditions, 6 and 12 months after RAI. Results were analysed in the whole group of patients and then separately in those who received one single ablative treatment (‘Single’ group, n = 10) and those who received multiple treatments (‘Multiple’ group, n = 10). Results In basal conditions, 3 of 20 (15%) patients had a reduced sperm count and belonged to the ‘Multiple’ group. After RAI, an increase of FSH (8·8 ± 1·2 UI/l vs 5·2 ± 1·2, P