Progesterone inhibits prolactin and growth hormone release from fowl pituitary glandsin vitro

Abstract

After preincubation of anterior pituitary glands of broiler fowls for 20 h in medium alone or medium containing progesterone, their responsiveness to hypothalamic stimulation and to TRH was determined. Following exposure to progesterone the basal rate of release of prolactin was reduced in a concentration-related manner but basal growth hormone release was unaffected. Stimulation of the release of prolactin and growth hormone by hypothalamic extract and TRH was reduced following incubation with progesterone, and the reduction of the prolactin response to TRH was related to progesterone concentration.