What stimulates the release of aldosterone from the adrenal cortex?

The release of aldosterone from the adrenal cortex is primarily stimulated by angiotensin II. This peptide hormone is a key component of the renin-angiotensin-aldosterone system (RAAS), which regulates blood pressure and fluid balance. When blood pressure drops or there is a decrease in sodium concentration, the kidneys release renin, which then converts angiotensinogen from the liver into angiotensin I. This is further converted to angiotensin II by angiotensin-converting enzyme (ACE), primarily in the lungs.

Angiotensin II has multiple physiological effects, one of which is to stimulate the adrenal cortex to release aldosterone. Aldosterone increases sodium reabsorption in the kidneys, which in turn increases blood volume and blood pressure. Thus, the role of angiotensin II is crucial in the regulation of aldosterone secretion and overall fluid balance in the body.

While factors like hypokalemia and ACTH can also influence aldosterone levels, they are not the primary regulators. Hypokalemia can stimulate aldosterone release, but its main trigger is not as direct as the action of angiotensin II. ACTH does play a role in stimulating adrenal function but is more relevant for cortisol release than for aldosterone.