In Addison's disease, which electrolyte changes are expected?

• A. Hyponatremia and hyperkalemia
• B. Hypernatremia and hypokalemia
• C. Hypercalcemia and hypophosphatemia
• D. Hypermagnesemia and hyponatremia

Answer: (A)

Addison's disease causes a deficiency of aldosterone, a mineralocorticoid that promotes sodium reabsorption and potassium excretion in the kidneys. Without aldosterone, the kidneys lose sodium (and water) leading to hyponatremia and volume depletion, while potassium is not excreted efficiently, causing hyperkalemia. This combination—low sodium and high potassium—is the characteristic electrolyte pattern. The other options describe electrolyte shifts that don’t align with aldosterone deficiency, such as high sodium with low potassium or calcium/magnesium abnormalities that aren’t typical findings in primary adrenal insufficiency.