The
prolactin response to TRH in a group of patients with
Kallmann's syndrome was found to be significantly lower compared to a group of hypergonadotrophic hypogonadal patients. Since levels of testicular products are comparably low in both groups, we hypothesize that high endogenous
LHRH production might be associated with an increased
prolactin response to TRH. In support of this, we were, indeed, able to establish a positive correlation between the magnitude of the
prolactin response to TRH and basal and
LHRH-stimulated LH/FSH levels (the latter serving as an index of endogenous
LHRH production) in: (1) eugonadal
men, (2) men with
Kallmann's syndrome, (3) oestrogen-treated agonadal men, (4) men with severely impaired spermatogenesis and, (5) agonadal men. A direct relation between
LHRH and the
prolactin response to TRH was demonstrated in a group of eugonadal men, the
prolactin response to TRH being greater after prolonged
LHRH pretreatment. We speculate that an increase of endogenous or exogenous
LHRH might be associated with decreased hypothalamic
dopamine secretion which could directly increase
prolactin synthesis. Indirectly, decreased
dopamine secretion could augment the potency of TRH in releasing
prolactin.