A 52-year-old man shows signs of hypertension and hypokalemia. Which of the following conditions is most likely causing his hypertension?

The presence of hypertension and hypokalemia in this patient strongly suggests hyperaldosteronism as the underlying condition. Hyperaldosteronism, often caused by adrenal adenomas or bilateral adrenal hyperplasia, leads to excessive secretion of aldosterone, a hormone that regulates sodium and potassium balance. Increased aldosterone levels promote sodium reabsorption in the kidneys, leading to increased blood volume and subsequently, hypertension. Concurrently, this condition promotes the excretion of potassium, resulting in hypokalemia.

In the context of the other conditions listed, Addison's disease typically presents with low blood pressure and hyperkalemia due to insufficient aldosterone production. Chronic kidney disease may cause hypertension but is not characteristically associated with hypokalemia; rather, it often leads to hyperkalemia as kidney function deteriorates. Cushing's disease, which also can cause hypertension, typically results in either normal or high potassium levels, and hypokalemia is not a prominent feature unless specific conditions such as adrenal tumors are present.

Therefore, the combination of hypertension and hypokalemia aligns most closely with hyperaldosteronism, making it the most likely cause in this scenario.