Effect of Pregnancy on the Somatotroph and the Prolactin Cell of the Human Adenohypophysis

Abstract

Human anterior pituitary glands from both sexes ranging in age from fetuses through elderly subjects, as well as pregnant and post-partum cases, were studied using a modification of Brookes' stain (Carmoisine L and orange G) that can distinguish 2 types of acidophil cells. The large-granuled, irregularly shaped, “carmoisinophilic” prolactin cell is present in significant numbers only in pregnancy and the postpartum period. There is a concomitant fall in the number of organeophilic somatotrophs in these groups. A few “mixed” cells containing both types of granules were seen. The data did not support or refute the concept that the prolactin cell is derived from the somatotroph. However, an alternative explanation should be considered, namely, that the somatotroph is inhibited by the production of large amounts of chorionic “growth hormone-prolactin” (placental lactogen); this suppression may continue for some time after delivery. The lack of suppression of the prolactin cell by placental lactogen may be explained by the differences in the type of hypothalamic control exerted on the production and release of growth hormone and prolactin.