Which statement best describes aldosterone's role in fluid and electrolyte balance?

• A. It promotes sodium and water reabsorption and potassium excretion.
• B. It promotes potassium reabsorption.
• C. It inhibits sodium reabsorption.
• D. It stimulates glucose uptake in muscles.

Answer: (A)

Aldosterone acts on the kidney’s distal tubules and collecting ducts to increase sodium reabsorption. It also promotes potassium excretion. Water follows sodium by osmosis, so sodium reabsorption leads to increased fluid volume. This combination—sodium reabsorption with accompanying water retention and potassium loss—best describes aldosterone’s role in regulating fluid and electrolyte balance.

Potassium reabsorption isn’t promoted by aldosterone; it is excretion that increases. Inhibiting sodium reabsorption would reduce fluid retention, which is opposite of aldosterone’s action. And aldosterone has no role in stimulating glucose uptake in muscles—that function is insulin-related.