Which serum electrolyte abnormality is most characteristic of hyperaldosteronism?

• A. Hypernatremia
• B. Hyponatremia
• C. Hypokalemia
• D. Hyperkalemia

Answer: (C)

The key idea is that excess aldosterone drives potassium loss in the kidneys. In hyperaldosteronism, aldosterone acts on the distal tubules to reabsorb sodium and excrete potassium (and hydrogen ions). This typically raises sodium levels and blood pressure, and most characteristically lowers serum potassium, leading to hypokalemia. The low potassium can cause weakness, fatigue, and arrhythmias if severe. Hyponatremia would not fit with aldosterone’s sodium-retaining effect, and hyperkalemia would be the opposite of what occurs with excess aldosterone. So, the serum electrolyte abnormality that best fits hyperaldosteronism is hypokalemia.