Aldosterone

Aldosterone’s main function is to regulate electrolyte and fluid balance by increasing sodium reabsorption and potassium excretion in the kidney’s distal tubules and collecting ducts. By promoting sodium (and thus water) retention and stimulating Na+/K+ ATPase and ENaC channels, it helps maintain blood volume and blood pressure. It is a key hormone in the renin–angiotensin–aldosterone system.

ADH (antidiuretic hormone) is released from the posterior pituitary in response to high plasma osmolality or low blood pressure; it increases water reabsorption via V2 receptors in renal collecting ducts, concentrating urine. Aldosterone is a steroid from the adrenal cortex (zona glomerulosa), stimulated by angiotensin II or high potassium; it promotes sodium reabsorption and potassium excretion in the distal nephron, raising blood volume and pressure.

High aldosterone causes the kidneys to retain sodium and water while excreting potassium, leading to hypertension, fluid overload, low potassium (hypokalemia) with muscle weakness, cramps, and palpitations, and metabolic alkalosis. Chronic excess raises risk of cardiovascular disease and kidney damage. Common causes include adrenal adenoma or hyperplasia; prompt diagnosis and treatment prevent complications.

Aldosterone is secreted by the adrenal glands, specifically by the zona glomerulosa of the adrenal cortex. This mineralocorticoid hormone regulates sodium and potassium balance, blood volume, and blood pressure by promoting renal sodium reabsorption and potassium excretion. Its release is primarily stimulated by the renin–angiotensin–aldosterone system and by elevated serum potassium levels.

Key triggers of aldosterone secretion include activation of the renin–angiotensin system—especially angiotensin II when renal perfusion or blood volume falls—and elevated plasma potassium. Other stimulants are sympathetic activation and, to a lesser extent, ACTH. Conditions such as low sodium, dehydration, heart failure, and certain diuretics or drugs that raise renin also increase aldosterone production.

Several hormones raise blood pressure. Angiotensin II is a potent vasoconstrictor that increases vascular resistance and stimulates aldosterone release, which promotes sodium and water retention. Adrenaline and noradrenaline increase heart rate, contractility and cause vasoconstriction. Vasopressin (antidiuretic hormone) increases water reabsorption and vascular tone. Together these hormones elevate arterial blood pressure.