Endocrine effects of vasectomy in man.

Serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T) and free testosterone index (FTI) were measured serially in 11 fertile men, ages 25 to 40, 4 weeks before to 40 weeks after elective vasectomy. During the 1st week postvasectomy there was a significant fall in FSH levels (P less than 0.001) and FTI (P less than 0.05), with recovery by 2 weeks. This acute response may be due to general surgical stress. Thereafter, the over-all mean FSH level was significantly (P less than 0.05) below the prevasectomy level; over-all levels of LH, T, and FTI did not change. We speculate that this decline in mean FSH levels is compatible with the existence of an as yet unidentified T-independent testicular factor influencing FSH production.