Aldosterone

Aldosterone is a hormone produced by the adrenal glands, specifically the adrenal cortex, which is located on top of the kidneys.

Function

Aldosterone plays a crucial role in regulating the body’s electrolyte balance, mainly by influencing the reabsorption of sodium and excretion of potassium in the kidneys. It helps maintain blood pressure, blood volume, and pH levels within a narrow range.

Production

Aldosterone is synthesized and released by the zona glomerulosa cells of the adrenal cortex in response to signals from the renin-angiotensin-aldosterone system (RAAS). This system is activated when there is a decrease in blood volume or low sodium levels in the blood.

Mechanism of Action

Once released, aldosterone binds to mineralocorticoid receptors located on the cells in the distal tubules and collecting ducts of the kidneys. This binding promotes the reabsorption of sodium ions from the urine back into the bloodstream while facilitating the excretion of potassium ions. Water follows the reabsorbed sodium, helping to maintain proper blood volume and blood pressure.

Regulation

The release of aldosterone is primarily regulated by the renin-angiotensin-aldosterone system, which is activated in response to low blood pressure, low blood sodium levels, or high blood potassium levels. Other factors, such as elevated levels of adrenocorticotropic hormone (ACTH) and certain electrolyte imbalances, can also influence aldosterone production.

Effects

Aldosterone’s main effects include:

• Promoting the reabsorption of sodium and water
• Increasing blood volume and blood pressure
• Facilitating the excretion of potassium
• Stimulating hydrogen ion secretion to regulate blood pH
• Indirectly affecting calcium and magnesium levels by modulating their reabsorption