The effect of prolactin on androgen response to human chorionic gonadotropin in normal men

Testicular androgen responses to human chorionic gonadotropin (hCG) were compared in normal males before and after suppression of prolactin (PRL) secretion with bromocriptine. Baseline follicle-stimulating hormone, luteinizing hormone, and PRL levels were suppressed by bromocriptine, 2.5 mg daily (P < 0.05). Serum testosterone and dihydrotestosterone (DHT) levels were reliably increased by one intramuscular injection of hCG (P < 0.05). Although testosterone responses to hCG were not significantly different in normal PRL and suppressed PRL cycles (P > 0.05), the DHT response was significantly increased in the suppressed cycle (P < 0.05), suggesting a physiologic 5 alpha-reductase blockage by PRL in men.