A 34-year-old man is referred for evaluation of hypeension and persistent hypokalemia in spite of taking oral potassium supplements. Blood pressure is 180/110 mm Hg. Serum sodium is 149 mEq/L (normal 140 to 148 mEq/L); potassium, 3.3 mEq/L (normal 3.6 to 5.2 mEq/L); Bicarbonate, 29 mEq/L (normal 22 to 29 mEq/L); Chloride, 103 mEq/L (normal 98 to 107 mEq/L); and Urea nitrogen, 23 mg/dL (normal 7 to 18 mg/ dL). Computed tomography demonstrates a 3-cm mass in the right adrenal gland. The most likely diagnosis is

**Core Concept**
The patient's presentation of hypertension, hypokalemia, and an adrenal mass suggests an excess of aldosterone, a mineralocorticoid hormone produced by the adrenal cortex. Aldosterone regulates sodium and potassium balance, and its excess can lead to hypertension and hypokalemia.

**Why the Correct Answer is Right**
The patient's serum sodium is elevated, and potassium is low, indicating an excess of aldosterone, which promotes sodium retention and potassium excretion. The elevated bicarbonate level also supports this diagnosis, as aldosterone stimulates the kidneys to retain bicarbonate. The computed tomography finding of an adrenal mass is consistent with an aldosterone-producing adenoma (APA), which is a benign tumor of the adrenal gland.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not provide a clear diagnosis and is too vague to be a correct answer.

**Option B:** Pheochromocytoma is a tumor of the adrenal medulla that produces catecholamines, not aldosterone. It would present with symptoms such as hypertension, tachycardia, and sweating, but not typically with hypokalemia.

**Option C:** Cushing's syndrome is caused by excess cortisol, which can lead to hypertension and hypokalemia, but it would also cause other symptoms such as weight gain, buffalo hump, and purple striae.

**Option D:** Renal artery stenosis can cause hypertension, but it would not cause hypokalemia or an elevated bicarbonate level.

**Clinical Pearl / High-Yield Fact**
Aldosterone-producing adenomas (APAs) are a common cause of primary aldosteronism, which is often referred to as "Conn's syndrome." APAs are usually benign and can be treated with surgery.

**Correct Answer:** C.

✓ Correct Answer: A. Conn syndrome