Anterior Pituitary and Pars Intermedia Space: Corticotrophs (ACTH) and Melanotrophs (α-MSH)

Abstract Proopiomelanocortin (POMC)-producing cells in the pituitary gland are central to the control of several physiologic functions, including stress, pigmentation, and analgesia. Two populations of cells, the corticotrophs of the anterior pituitary and the melanotrophs of the pars intermedia, differentially posttranslationally process POMC to produce ACTH and α-MSH, respectively. ACTH acts at the adrenal gland to control production and secretion of glucocorticoids, while α-MSH is important for the control of pigmentation. These two cell populations are under hypothalamic control, either through release of hypothalamic hormones into the portal vasculature (corticotrophs) or through direct innervation (melanotrophs). Pulsatile release of ACTH and glucocorticoids has been well characterized in humans and rodents, and it is important for their physiologic function, while the precise pattern of α-MSH release and its impact on its function is not well explored. Because of the pleiotropic effects of glucocorticoids, conditions associated with either under- or overproduction of the stress hormones have particularly deleterious effects; therefore, better understanding of the control of ACTH and glucocorticoids production is important for both diagnoses and treatment of a wide variety of disorders.