It is a steroid hormone secreted by the adrenal glands.
Aldosterone serves as the primary regulator of water and salt balance in the body and, therefore, is classified as a mineralocorticoid. It also has a negligible effect on the metabolism of fats, carbohydrates, and proteins, which impacts blood pressure.
Aldosterone has a plasma half-life of fewer than 20 minutes.
Function of aldosterone
It plays a central role in regulating blood pressure mainly by acting on organs like the kidney and colon.
It is essential for preserving sodium in the kidney, the salivary glands, and the sweat glands.
It plays a central role in the homeostatic regulation of blood pressure and plasma levels of sodium and potassium. It does so mainly by acting on the mineralocorticoid receptors in the distal tubules and the collecting ducts of the nephron.
Aldosterone is responsible for the reabsorption of approximately 2% of the filtered sodium in the kidneys, almost equal to the total sodium content in human blood under average glomerular filtration rates.
It also influences the excretion of potassium from the kidney, which indirectly affects the retention or loss of water, blood pressure, and blood volume.
Aldosterone is synthesized from corticosterone, a steroid derived from cholesterol. The renin-angiotensin system regulates aldosterone production in the adrenal cortex’s glomerulosa zone.
Renin is secreted from the kidneys in response to variations in blood pressure and volume and plasma levels of sodium and potassium.
Renin acts on a protein circulating in the plasma called angiotensinogen, which divides this substance into angiotensin I. Angiotensin I is subsequently converted to angiotensin II, which stimulates the release of aldosterone from the adrenal glands.
Mechanism of action
It acts by binding and activating a receptor in the cytoplasm of renal tubular cells. The activated receptor then stimulates the production of ion channels in renal tubular cells, which increases the reabsorption of sodium in the blood and increases the excretion of potassium in the urine.
How is aldosterone controlled?
Medications that interfere with the secretion or action of aldosterone are used as antihypertensives, such as lisinopril, which lowers blood pressure by blocking the angiotensin-converting enzyme, leading to decreased secretion of aldosterone.
These medications stimulate sodium and water excretion in the urine while blocking the excretion of potassium.
When deregulated, aldosterone is pathogenic and contributes to cardiovascular and renal disease development and progression.
What happens if there are high levels of aldosterone?
The most common cause of high aldosterone levels is overproduction, often of a small benign adrenal tumor ( primary hyperaldosteronism ). Symptoms include high blood pressure, low potassium levels, and an abnormal increase in blood volume.
What happens if there are low levels of aldosterone?
Low aldosterone levels are found in a rare condition called Addison’s disease.