Effects of progesterone administration on follicle-stimulating hormone and prolactin release in estrogen treated eugonadal adult men.

In order to investigate the modulatory effect of steroids on FSH secretion in vivo, we studied 16 human males, aged 51-81 years, affected by prostatic carcinoma. They were given estradiol or E2 plus progesterone (P), added at different times during E2 treatment. Daily blood samples were collected in order to determine LH, FSH, and PRL levels; moreover, blood samples were collected at 2 h intervals for 12 h on the day of P administration. We observed the expected biphasic effect on LH secretion, whereas daily basal FSH levels, during E2 treatment, decreased gradually and progressively from the first day until the end of the study. FSH levels exhibited, after P administration, wide fluctuations, with peak levels observed from 2 to 6 h after P in 4 of 6 patients studied (at 72 h during E2 treatment). A clear trend toward FSH increase was also observed in 3 out of 5 patients in whom P was administrated 96 h after starting E2 administration. In this case, FSH increases were delayed, becoming evident between 8th and 10th h after P injection. Finally, during E2 administration basal PRL levels showed a progressive increase, which was significant in all three groups. In conclusion, these data confirm the biphasic effects of estrogen administration on LH secretion in eugonadal adult human males; while estrogens alone showed an inhibitory effect on FSH secretion, the addition of P induced also a positive action, resulting in a clear FSH peak in some patients tested. The time course of E2 and P administration seems to be critical for the hormone response pattern.(ABSTRACT TRUNCATED AT 250 WORDS)