Chapter 8: The Adrenal Cortex

The Adrenal Cortex details the structural and functional distinctions between the adrenal medulla and the three cortical layers: the zona glomerulosa, which produces the mineralocorticoid aldosterone under the regulation of the renin–angiotensin system; and the zona fasciculata and reticularis, which secrete glucocorticoids like cortisol and androgens such as androstenedione under the control of the hypothalamic–pituitary–adrenal (HPA) axis. The text provides an in-depth analysis of the feedback mechanisms involving corticotrophin-releasing hormone (CRH) and adrenocorticotrophic hormone (ACTH), emphasizing the significance of circadian rhythms and the physiological response to physical and mental stress. Significant attention is given to adrenocortical hyperfunction, specifically Cushing’s syndrome, where the discussion differentiates between pituitary-dependent Cushing’s disease, ectopic ACTH production, and autonomous adrenal tumors. The chapter also addresses primary adrenocortical hypofunction, known as Addison’s disease, and secondary adrenal insufficiency, highlighting the life-threatening risks of an adrenal crisis characterized by severe electrolyte imbalances like hyponatraemia and hyperkalaemia. Diagnostic protocols are thoroughly examined, including the use of dexamethasone suppression tests, Synacthen (tetracosactide) stimulation tests, and aldosterone-to-renin ratios. Furthermore, it covers congenital adrenal hyperplasia (CAH), focusing on enzyme deficiencies such as 21-alpha-hydroxylase that lead to virilization and salt-wasting, and primary hyperaldosteronism (Conn’s syndrome) as a critical cause of secondary hypertension and metabolic alkalosis.