Aldosterone

Definition

Aldosterone is a steroid hormone produced by the adrenal glands that plays a key role in regulating sodium and potassium balance, as well as blood pressure. It primarily acts on the kidneys to promote sodium reabsorption and potassium excretion, which helps maintain fluid balance and electrolyte homeostasis in the body.

5 Must Know Facts For Your Next Test

1. Aldosterone is primarily produced in the zona glomerulosa of the adrenal cortex and is part of the renin-angiotensin-aldosterone system (RAAS).
2. Its main function is to increase sodium reabsorption in the distal tubules and collecting ducts of the kidneys, which leads to water retention and increased blood volume.
3. The secretion of aldosterone is stimulated by factors such as low blood pressure, low sodium levels, and high potassium levels in the blood.
4. Aldosterone helps maintain potassium homeostasis by promoting its excretion through the kidneys, preventing hyperkalemia (high potassium levels).
5. Dysregulation of aldosterone secretion can lead to conditions such as hyperaldosteronism, contributing to hypertension and electrolyte imbalances.

Review Questions

• How does aldosterone influence sodium and potassium balance in the body?
  • Aldosterone influences sodium and potassium balance by promoting sodium reabsorption in the kidneys while facilitating potassium excretion. When aldosterone levels rise, the distal tubules and collecting ducts of the nephron increase their permeability to sodium, allowing more sodium to be absorbed back into the bloodstream. Concurrently, potassium ions are secreted into the urine for excretion. This process helps maintain fluid balance, blood volume, and proper electrolyte concentrations.
• Discuss the role of angiotensin II in regulating aldosterone secretion and its impact on blood pressure.
  • Angiotensin II plays a crucial role in regulating aldosterone secretion by stimulating its release from the adrenal glands. When blood pressure drops or sodium levels are low, renin is released from the kidneys, converting angiotensinogen to angiotensin I, which is then converted to angiotensin II. Angiotensin II not only triggers aldosterone release but also causes vasoconstriction of blood vessels, resulting in an increase in blood pressure. This dual action underscores how aldosterone is essential for restoring normal blood pressure levels.
• Evaluate how diuretics can affect aldosterone activity and overall fluid balance in patients with hypertension.
  • Diuretics can significantly affect aldosterone activity by promoting the excretion of sodium and water from the body, thereby reducing blood volume. In patients with hypertension, diuretics help lower blood pressure by counteracting some effects of aldosterone. However, long-term use can lead to a compensatory increase in aldosterone secretion due to decreased sodium levels. This feedback mechanism can sometimes limit the effectiveness of diuretics and necessitate monitoring potassium levels to prevent complications such as hypokalemia (low potassium levels) or hyperkalemia if renal function is compromised.

Related terms

Renin: An enzyme secreted by the kidneys that initiates the renin-angiotensin-aldosterone system (RAAS), leading to aldosterone release and regulation of blood pressure.

Angiotensin II: A peptide hormone that stimulates aldosterone secretion from the adrenal glands and causes vasoconstriction, which raises blood pressure.

Diuretics: Medications that promote the excretion of water and electrolytes through urine, often used to treat high blood pressure and fluid retention, affecting aldosterone's action.