This document discusses aldosterone, a steroid hormone that regulates electrolyte and fluid balance. It is synthesized in the adrenal cortex and works by increasing sodium absorption and potassium secretion in the kidneys, salivary glands, and gastrointestinal tract. Aldosterone secretion is primarily regulated by angiotensin II through the renin-angiotensin-aldosterone system. This system controls blood pressure by stimulating aldosterone release in response to decreases in blood volume or pressure. Aldosterone antagonists and ACE inhibitors are used to treat hypertension by blocking the effects of aldosterone or inhibiting angiotensin II formation, respectively.