Aldosterone

Aldosterone is a steroid hormone that is produced and secreted in the zona glomerulosa of the adrenal cortex. It is the main mineralocorticoid, whose precursor molecule is cholesterol. Aldosterone is transported in the plasma either free or bound to plasma proteins, its effect in the target tissue is mediated by nuclear receptors. Aldosterone secretion increases due to hyperkalemia and angiotensin II. Conversely, a slight decrease in aldosterone secretion is caused by hypernatremia. The presence of adrenocorticotropic hormone (ACTH) is essential for aldosterone secretion, but has little regulatory significance.

adrenal gland

kidneys, sweat and salivary glands, intestine

regulation of natremia, potassium and ECT volume

Function

Scheme of steroidogenesis

The level of plasma aldosterone is low, usually around 0.17 nmol/l. The hormone is the main regulator of natremia, potassium and extracellular fluid volume.

Effects of aldosterone

It acts mainly in the kidneys (distal tubule), then in the sweat and salivary glands and in the intestine. In the target organs, it supports the resorption of Na⁺ by binding to cell receptors in the collecting ducts and in the distal tubules. Aldosterone-stimulated Na⁺ resorption is accompanied by water resorption (passively, following an osmotic gradient), leading to an increase in extracellular fluid volume and a consequent increase in blood pressure. It also stimulates the excretion of K⁺ in the kidneys.

Links

Related articles

• Renin-angiotensin-aldosterone system
• ADH

Bibliography

• GANONG, William F. Přehled lékařské fyziologie. 20. edition. Praha : Galén, 2005. 890 pp. ISBN 80-7262-311-7.