Effect of an LHRH agonist on pituitary and testicular function in rhesus monkeys

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Abstract
Male rhesus monkeys were given 100 .mu.g [(imBzl)-D-His6,Pro9-NEt]-LHRH (LHRH-A), a potent LHRH agonist, s.c. daily for 40 wk. The 1st dose of LHRH-A caused acute increases (2-4 h after injection) in serum LH [luteinizing hormone] (50-fold), FSH (2.5-fold) and testosterone (15-fold) concentrations. Chronic treatment led to a 95% decrease in LH and FSH responses. In spite of a marked decrease in LH response the effect on testosterone response was less evident. Administration of 50 i.u. hCG [human chorionic gonadotropin] to control and LHRH-A-treated animals showed that the testicular steroidogenic response was unimpaired by the chronic treatment. Evaluation of the electroejaculated semen at regular intervals showed that there was no consistent reduction in the sperm count of LHRH-A-treated monkeys. Testicular biopsies showed that normal spermatogenesis was occurring in all treated animals, but testicular volume was significantly decreased. In rhesus monkeys, the pituitary apparently is more susceptible to desensitization by chronic LHRH agonist treatment than are the testes. LHRH agonists evidently do not have direct antitesticular effect in rhesus monkeys [These peptides may provide a new approach to regulating fertility in men].

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