Question

Which of these is most often secreted by a pheochromocytoma?

• A. Epinephrine
• B. Norepinephrine
• C. Dopamine
• D. Serotonin

Hint:

Pheochromocytoma cells often skip the last conversion step, so this catecholamine builds up and dominates.

Answer 1

The Correct Option is B

Step 1: Recall what a pheochromocytoma is.
A pheochromocytoma is a tumor of the chromaffin cells of the adrenal medulla. These are the same cells that normally make and release catecholamines, so the tumor keeps making them, often in large and uncontrolled amounts.

Step 2: Recall which catecholamine dominates.
The normal adrenal medulla makes mostly epinephrine, using the enzyme PNMT to convert norepinephrine into epinephrine. In a pheochromocytoma, tumor cells often lose this efficient conversion step, so norepinephrine builds up and becomes the catecholamine secreted in the largest amount overall, causing sustained high blood pressure.

Step 3: Check why epinephrine is not the best answer.
Epinephrine is still released by many pheochromocytomas and causes the classic episodic palpitation and sweating attacks, but taken across all pheochromocytomas, norepinephrine is secreted more often and in greater total amount, and this is what the question is testing.

Step 4: Check why dopamine is wrong.
Dopamine is the catecholamine precursor and is raised mainly in malignant or extra-adrenal pheochromocytomas (paragangliomas), not in typical benign adrenal tumors, so it is not the usual main secretion.

Step 5: Check why serotonin is wrong.
Serotonin is not a catecholamine at all. It is the hormone secreted by carcinoid tumors of the gut, which cause flushing and diarrhea, a completely different tumor and a different clinical picture.

Step 6: Final answer.
The catecholamine most often secreted by a pheochromocytoma is norepinephrine.