Which statement best describes the action of aldosterone in fluid and electrolyte balance?

Which statement best describes the action of aldosterone in fluid and electrolyte balance?

• A. Aldosterone promotes renal reabsorption of sodium and water and excretion of potassium and hydrogen ions
• B. Aldosterone increases calcium absorption in the gut
• C. Aldosterone stimulates glucose production in the liver
• D. Aldosterone modulates immune response

Answer: (A)

Aldosterone acts on the distal nephron to promote sodium reabsorption, and where sodium goes, water tends to follow, increasing blood volume. At the same time, it increases the excretion of potassium and hydrogen ions into the urine. This happens mainly in the collecting ducts and late distal tubules: aldosterone increases the number and activity of epithelial sodium channels and Na+/K+-ATPase pumps in principal cells, driving sodium reabsorption and potassium secretion. Hydrogen ion secretion by intercalated cells also rises, which can influence acid-base balance. This combination—sodium and water retention with potassium and hydrogen ion loss—is how aldosterone helps regulate fluid status, blood pressure, and electrolyte balance. The other statements don’t reflect aldosterone’s primary role. Calcium absorption in the gut is more closely tied to vitamin D and parathyroid hormone. Glucose production in the liver is a glucocorticoid effect (like cortisol). Immune modulation is also more associated with glucocorticoids.

Aldosterone acts on the distal nephron to promote sodium reabsorption, and where sodium goes, water tends to follow, increasing blood volume. At the same time, it increases the excretion of potassium and hydrogen ions into the urine. This happens mainly in the collecting ducts and late distal tubules: aldosterone increases the number and activity of epithelial sodium channels and Na+/K+-ATPase pumps in principal cells, driving sodium reabsorption and potassium secretion. Hydrogen ion secretion by intercalated cells also rises, which can influence acid-base balance. This combination—sodium and water retention with potassium and hydrogen ion loss—is how aldosterone helps regulate fluid status, blood pressure, and electrolyte balance.

The other statements don’t reflect aldosterone’s primary role. Calcium absorption in the gut is more closely tied to vitamin D and parathyroid hormone. Glucose production in the liver is a glucocorticoid effect (like cortisol). Immune modulation is also more associated with glucocorticoids.