A 34-year-old man complains of sudden attacks of dizziness, blurred vision, and excruciating headaches of 4 months in duration. During one of these attacks, his blood pressure was 180/120 mm Hg. The patient’s father had been treated for thyroid cancer about 15 years ago. Laboratory studies show normal serum levels of aldosterone, renin, and angiotensin. A 24-hour urinalysis reveals increased metanephrines. Episodic hypertension in this patient is most likely caused by a tumor in which of the following endocrine organs?

**Core Concept**
The patient's symptoms and laboratory findings are suggestive of episodic hypertension, which is a hallmark of a specific endocrine disorder. The increased metanephrines in the 24-hour urinalysis point towards an excess of catecholamines, which are neurotransmitters involved in the body's fight-or-flight response.

**Why the Correct Answer is Right**
The patient's symptoms, including sudden attacks of dizziness, blurred vision, and excruciating headaches, are consistent with pheochromocytoma, a type of tumor that secretes excess catecholamines. The episodic hypertension, as seen during one of the patient's attacks, is a classic manifestation of this condition. The increased metanephrines in the urinalysis confirm the diagnosis, as metanephrines are metabolites of catecholamines. Pheochromocytomas are often associated with a family history of similar tumors, which may explain the patient's father having been treated for thyroid cancer (a possible indication of a genetic predisposition to endocrine tumors).

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because aldosterone-secreting tumors (Conn's syndrome) typically present with hypokalemia and hypertension, but the patient's laboratory studies show normal serum aldosterone levels.

**Option B:** This option is incorrect because thyroid cancer is not directly associated with episodic hypertension or increased metanephrines.

**Option C:** This option is incorrect because multiple endocrine neoplasia (MEN) syndromes can involve various endocrine organs, but the patient's symptoms and laboratory findings are most consistent with pheochromocytoma.

**Clinical Pearl / High-Yield Fact**
When suspecting a pheochromocytoma, it's essential to obtain a 24-hour urine collection for metanephrines or catecholamines to confirm the diagnosis. The patient should be advised to avoid any strenuous activity or emotional stress during the collection period, as these can increase catecholamine secretion.

**Correct Answer:** C.

✓ Correct Answer: A. Adrenal