Professional and Linguistic Assessments Board (PLAB) Practice Exam

What electrolyte imbalance is characteristic of hyperaldosteronism?

1. Hyperkalemia

2. Hypocalcemia

3. Hypokalemia

4. Hypophosphatemia

The correct answer is: Hypokalemia

In hyperaldosteronism, there is an overproduction of aldosterone, a hormone that plays a key role in regulating sodium and potassium levels in the body. Aldosterone promotes the reabsorption of sodium and the excretion of potassium in the kidneys. As a result, patients with hyperaldosteronism typically exhibit hypokalemia, which is a decrease in potassium levels in the blood. This imbalance occurs because the excessive aldosterone causes the kidneys to retain sodium, leading to an increase in blood volume and blood pressure, while simultaneously promoting the loss of potassium. Therefore, hypokalemia is characteristic of this condition, making it the correct answer. The other potential imbalances listed—hyperkalemia, hypocalcemia, and hypophosphatemia—do not directly relate to the effects of aldosterone. Hyperkalemia would be expected in conditions where potassium is not adequately excreted, which is the opposite of what occurs in hyperaldosteronism. Hypocalcemia and hypophosphatemia involve calcium and phosphate levels, which are not primarily regulated by aldosterone. Understanding the physiological role of aldosterone clarifies why hypokalemia is the hallmark electrolyte disturbance associated with hyperaldosteronism.