Prolactin and gonadal function.

In most cases, hypogonadism is found in patients with hyperprolactinaemia and galactorrhea, whatever the origin. Correlations between basal levels of gonadotrophins and prolactin have been studied during dynamic tests (LH/FSH-RH, TRH, hypoglycaemia) and after treatment with bromocriptine. There is no evidence for gonadotrophin deficiency associated with hyperprolactinaemia and it would appear that prolactin rather blocks the actions of the gonadotrophins at the gonadal level. Furthermore, an "in vitro" study showed that prolactin blocks the stimulant effect of gonadotrophin on steroidogenesis by the Graafian follicles. This phenomenon may be a mechanism of regulation of the menstrual cycle. The significance of these phenomena is discussed.