HYDROTESTOLACTONE LOWERS SERUM OESTRADIOL AND PRL LEVELS IN NORMAL MEN: EVIDENCE OF A ROLE OF OESTRADIOL IN PRL SECRETION*

Abstract

The effect on serum PRL [prolactin] levels of lowering serum estradiol (E2) concentration by short-term administration of an aromatase activity inhibitor, hydrotestolactone (HT), was studied in 6 healthy male subjects. After HT administration serum E2 levels decreased from 68 .+-. 5.8 to 26 .+-. 2.5 pmol/l (mean .+-. SE, P < 0.05). These E2 changes were accompanied by a significant decrease in mean 2 h PRL levels from 11.2 .+-. 2.1 to 6.5 .+-. 1.6 ng/ml mean .+-. SE, P < 0.05). The evaluation of individual percentage change from basal concentrations showed a varying decrease in all subjects. Apparently under physiological conditions, E2 may be one of the factors which control blood PRL concentrations in men.