Which is the most common clinical feature of pheochromocytoma?
**Core Concept**
Pheochromocytoma is a rare, usually benign tumor of the adrenal gland that secretes excess catecholamines, leading to various systemic effects. The most common clinical feature of pheochromocytoma is episodic hypertension, which can be severe and debilitating.
**Why the Correct Answer is Right**
The episodic hypertension in pheochromocytoma is primarily due to the excessive release of catecholamines, such as adrenaline (epinephrine) and noradrenaline (norepinephrine), from the tumor. These hormones cause vasoconstriction and increase cardiac output, resulting in elevated blood pressure. The episodic nature of the hypertension is due to the intermittent release of catecholamines from the tumor, which can be triggered by various stimuli such as stress, exercise, or certain medications.
**Why Each Wrong Option is Incorrect**
**Option A:** Headache - While headache is a common symptom of pheochromocytoma, it is not the most common clinical feature. Headache is often a result of the episodic hypertension and can be severe, but it is not as specific or sensitive as hypertension.
**Option B:** Sweating - Sweating is a symptom of pheochromocytoma, but it is not as common as hypertension. Sweating is often a result of the excessive catecholamines released from the tumor.
**Option C:** Weight loss - Weight loss is a possible symptom of pheochromocytoma, but it is not the most common clinical feature. Weight loss can occur due to various factors, including the excessive catecholamines released from the tumor, but it is not as specific or sensitive as hypertension.
**Clinical Pearl / High-Yield Fact**
The "rule of 10s" in pheochromocytoma is a useful mnemonic to remember the common symptoms of the disease: 10% of cases are bilateral, 10% are malignant, and 10% occur in children. Additionally, pheochromocytoma can be associated with other conditions, such as multiple endocrine neoplasia (MEN) syndromes, neurofibromatosis type 1, and von Hippel-Lindau disease.
**Correct Answer: C. Hypertension**