Adrenal Hormone Physiology

The adrenal glands sit above the kidneys, but each part answers to a different control system. That distinction explains why some patients lose cortisol and aldosterone together, while others have low cortisol with relatively preserved blood pressure and potassium. The adrenal cortex produces steroid hormones in three zones: - Zona glomerulosa produces aldosterone. It responds mainly to the renin–angiotensin–aldosterone system and serum potassium, not to ACTH. Aldosterone tells the distal nephron to retain sodium and excrete potassium. Water follows retained sodium, supporting extracellular fluid volume and blood pressure. - Zona fasciculata produces cortisol under hypothalamic-pituitary control. CRH stimulates ACTH release, and ACTH stimulates cortisol production. Cortisol normally rises before waking and increases sharply during illness, trauma, surgery, and other physiologic stress. - Zona reticularis produces adrenal androgens. The adrenal medulla is functionally part of the sympathetic nervous system. Chromaffin cells release epinephrine and norepinephrine when stimulated by sympathetic preganglionic neurons. Cortisol delivered from the cortex to the medulla helps support epinephrine synthesis, creating a local cortex-to-medulla partnership. Cortisol does more than regulate glucose. It supports gluconeogenesis, helps maintain vascular responsiveness...