Neurohormonal mechanisms controlling trophic hormone secretion of the anterior pituitary.

Anterior pituitary function is primarily controlled by neurohormonal mechanisms. The immediate control of trophic hormone secretion seems to be exercised by the medial basal hypothalamus, the hypophysiotrophic area, producing the hypothalamic releasing and inhibiting factors carried by the portal circulation to the adenohypophysis. This system is probably responsible for the maintenance of “basal” secretion of pituitary hormones. Normal function of the anterior lobe is controlled by neural elements outside the medial basal hypothalamus. This second control level presumably acts on the pituitary via the hypophysiotrophic area by modifying the synthesis and release of the hypothalamic releasing and inhibiting substances. The feedback action of hormones on the adenohypophysis appears to be mediated, at least partly, by way of the hypothalamic control mechanism.