Aldosterone is a steroid hormone produced by the adrenal glands that plays a critical role in regulating blood pressure, blood volume, and electrolyte balance. Its main functions include:
- Promoting the reabsorption of sodium (Na⁺) in the kidneys, specifically in the distal tubules and collecting ducts of the nephron. This sodium reabsorption leads to water retention because water follows sodium, which helps increase blood volume and blood pressure.
- Stimulating the excretion of potassium (K⁺) into the urine, thereby lowering potassium levels in the blood.
- Helping regulate acid-base balance by stimulating secretion of hydrogen ions (H⁺) in the kidney.
- Acting mainly through mineralocorticoid receptors in kidney cells to increase the expression of sodium channels and sodium-potassium pumps, which facilitate these effects.
- Contributing to electrolyte balance by increasing sodium and water reabsorption in other organs such as the colon, salivary glands, and sweat glands.
Aldosterone is a key component of the renin-angiotensin-aldosterone system (RAAS), which is activated when blood pressure falls. This system helps restore blood pressure to healthy levels by triggering aldosterone release and other mechanisms like blood vessel constriction. Overall, aldosterone conserves sodium and water to maintain blood pressure and volume while promoting potassium excretion to keep electrolyte levels balanced. It directly influences kidney function, blood pressure regulation, and fluid balance in the body. Dysregulation of aldosterone can lead to cardiovascular and kidney diseases.
