Aldosteron

Aldosteron

Aldosterone is a steroid hormone produced by the adrenal cortex in the adrenal glands located at the top of each kidney. It plays a central role in the regulation of blood pressure and the balance of sodium and potassium in the body. Aldosterone is part of the renin-angiotensin system (RAS), which is a major regulatory system of blood pressure and fluid balance.

Production and Regulation

Aldosterone is synthesized in the zona glomerulosa layer of the adrenal cortex. Its production is stimulated by several factors:

• The decrease in blood flow to the kidneys triggers the release of renin, a hormone that acts on the liver to produce angiotensinogen, which is then converted to angiotensin I. Angiotensin I is subsequently converted to angiotensin II by the enzyme angiotensin-converting enzyme (ACE), which is found in the lungs. Angiotensin II is a potent vasoconstrictor and stimulates the secretion of aldosterone.
• High potassium levels in the blood directly stimulate the adrenal cortex to produce aldosterone.
• The pituitary gland secretes adrenocorticotropic hormone (ACTH), which has a minor role in stimulating aldosterone production.

Function

Aldosterone acts mainly on the distal convoluted tubule and the collecting ducts of the nephron, the functional unit of the kidney. It increases the reabsorption of sodium and water and the excretion of potassium by these renal tubules. This action helps to increase the volume of extracellular fluid in the body, thereby increasing blood pressure. Aldosterone is crucial for maintaining sodium and potassium balance, which is essential for normal function of the muscles, nerves, and other systems in the body.

Pathophysiology

Abnormal levels of aldosterone can lead to several medical conditions:

• Hyperaldosteronism is a condition characterized by the overproduction of aldosterone, which can lead to high blood pressure and low blood potassium levels. It can be caused by an adrenal adenoma (primary hyperaldosteronism) or conditions that stimulate the adrenal glands to overproduce aldosterone (secondary hyperaldosteronism).
• Hypoaldosteronism refers to the inadequate production of aldosterone, which can result in low blood pressure and high blood potassium levels. This condition can be caused by adrenal insufficiency, certain genetic disorders, or medications that affect aldosterone production.

Clinical Significance

Aldosterone antagonists, such as spironolactone and eplerenone, are used to treat conditions like hypertension, heart failure, and hyperaldosteronism by blocking the effects of aldosterone. These medications help to reduce blood pressure and prevent the adverse cardiovascular effects associated with high aldosterone levels.

See Also

• Adrenal gland
• Renin-angiotensin system
• Hypertension
• Electrolyte imbalance