Suppression of spermatogenesis over two years in rhesus monkeys actively immunized with follicle-stimulating hormone

Active immunization of four adult rhesus monkeys with highly purified ovine follicle-stimulating hormone (FSH) resulted in the production of specific FSH antibodies and a suppression of spermatogenesis for the observation period of 2 years. Although testicular volume was markedly reduced, endocrine function did not appear to be affected. Serum testosterone and bioassayable LH levels as well as the frequency of spontaneous ejaculations were the same as in control animals. No adverse side effects were noted over the 2-year period. These results may encourage investigations on active immunization with FSH as a possible approach to male fertility control.