Chapter 3 - The hypothalamus and anterior pituitary

Abstract

The pituitary gland has often been called “the master gland” because so many important functions are governed by the hormones it secretes. In this chapter, readers see that the pituitary hormones are under the control of both the central nervous system, especially the hypothalamus and the secretions of the distal endocrine glands, and other internal signals. The hypothalamic releasing hormones function to control the secretions of the anterior pituitary hormones, either positively or negatively. The hormones secreted by the distal endocrine glands exert, in general, negative feedback effects in the brain and in the anterior pituitary. There are many signals originating either outside or inside the body that are mediated by the central nervous system. Thus changes in the environment can ultimately stimulate the secretion of hypothalamic releasing hormones, which, through their effects on pituitary hormonal secretion, allow the body to adapt to the change. Likewise, signals from within the organism can trigger this cascade system so that the secretion of hormones from distant target glands can be affected. The chapter covers control cascades; anatomical relationships; structure, synthesis, secretion, and target cells of the hypothalamic releasing hormones; chemistry of the anterior pituitary hormones; regulation and biological actions of growth hormone and prolactin; involvement of the hypothalamus in appetite regulation; and clinical aspects of the hypothalamus and pituitary.