Effects of sulpiride induced hyperprolactinemia on testosterone secretion and metabolism before and after HCG in normal men.

The purpose of the study was to investigate the effects of sulpiride-induced hyperprolactinemia on testicular functions, as assessed by evaluation of plasma testosterone (T), dihydrotestosterone (DHT) and 17 beta-estradiol (E2) levels. An HCG test (5000 IU on three consecutive days) was performed in basal conditions and after 12 and 26 days of sulpiride treatment (150 mg daily) in 7 male volunteers, 19 to 32 years of age, as well as in 6 sulpiride-free controls. The results show that after 12 days of induced hyperprolactinemia (mean increase 400%) the T response to HCG was similar to basal test; after 26 days however, the increase of T mean plasma levels was significantly greater. The increase in E2 significantly correlated to that of T during the first and second HCG tests, but no longer after 26 days of hyperprolactinemia, resulting in an imbalance of the E2/T ratio of plasma increments. The response of DHT to HCG was significant in basal conditions and after 26 days of sulpiride and always correlated with T behavior. Data obtained in our experimental conditions suggest that PRL might enhance T secretion. 5 alpha-reductase activity seemed to be partially affected after 12 days of treatment, while a significant inhibition seemed to be exerted on aromatase activity.