The effects of ovariectomy and estrogen treatment on the dopamine inhibition of gonadotropin and prolactin release.

The suppressive action of dopamine (DA) on circulating gonadotropin and PRL levels is found to be positively correlated with their basal serum concentrations. Thus, DA inhibition is greater in ovariectomized (agonadal) women than in normal women on day 2 of their menstrual cycles, and the reverse is observed for PRL. Pretreatment of agonadal subjects with estrogen lowers the basal levels of LH and FSH and thereby proportionately decreases the suppressive effects of DA. Estrogen treatment elevates the basal level of PRL in agonadal subjects and also the PRL-inhibiting effect of DA. These findings indicate that castration and estrogen treatment significantly influence the inhibitory effect of DA on gonadotropin and PRL release.