Adrenal zones, ACTH

Adrenocorticotropic Hormone (ACTH) (Corticotropin) Anterior Pituitary (Corticotroph) 39 aa 2p25 Stimulates steroidogenesis in all three zones of the adrenal cortex, thereby increasing secretion of cortisol, DHEAS, and aldosterone. Stimulated by CRH and inhibited by cortisol. 

ACTH acts mainly on the cells of the zona fasciculata of the adrenal cortex to stimulate the synthesis and release of cortisol (Chapter 32). It also stimulates the secretion of adrenal androgens from the zona reticularis. Binding of ACTH to receptors activates formation of cAMP, which mediates cortisol formation and secretion and protein synthesis. Deficiency of ACTH leads to reduction in size and activity of adrenocortical cells in the inner two zones. 

Cortisol is produced in the zona fasciculata and zona reticularis of the adrenal cortex, the end prixluct of a cascade of hormones which make up the hypothalamic-pituitary-adreniKortical axis (Fig. 2). Corticotrophin releasing hormone (CRH) is secreted by the hypothalamus under the influence of cerebral factors. Adrenocorticotrophic hormone (corticotrophin. orsimply ACTH) is secreted by the anterior pituitary under the control of CRH to maintain the fa.scicular and reticular zones of the adrenal cortex and to stimulate the secretion of cortisol. Ilypolhalamie secretion of CRH and pituitary secretion of ACTH are modulated by cortisol in negative feedback liwps. 

In the absence of the anterior pituitary and ACTH stimulation, the inner zones of the cortex atrophy, and the production of glucocorticoids and adrenal androgens is markedly impaired. Persistently elevated levels of ACTH, due either to repeated administration of large doses of ACTH or to excessive endogenous production, induce hyperplasia and hypertrophy of the inner cortical zones, with overproduction of cortisol and adrenal androgens. Adrenal hyperplasia is most marked... 

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