Summary
The present study examined the conditions under which LHRH is capable of releasing
PRL in the human male. No such effect was found in eugonadal males. After pretreatment
with 100 µg ethinyloestradiol/day, but not with 30 µg/day, the PRL-releasing action
of LHRH became apparent. This indicates that high doses of oestrogens are required.
This effect of LHRH on PRL release was still demonstrable two weeks after withdrawal
of oestrogens. This suggests that rather than oestrogens per se, alterations in the
control of PRL induced by oestrogens, render the lactotroph sensitive to LHRH. Further:
No effect was observed after administration of a bolus LHRH, whereas LHRH administered
as an infusion released PRL with a latency period of 20—40 minutes. The interpretation
for this could be that- LHRH acts indirectly via a LHRH-induced decreased dopaminergic
tone, which mechanism requires a certain amount of time.
It is hypothesised that a LHRH-induced decrease of dopaminergic tone together with
a weakened dopaminergic control of thé oestrogenised lactotroph could account for
this non-specific action of LHRH on PRL release.
Key Words
LHRH - Prolactin - Oestrogen