Final answer:
Vanillylmandelic acid (VMA) is the most common metabolite seen with pheochromocytoma. Pheochromocytoma is a tumor of the adrenal medulla that causes excessive production of catecholamines, which are then metabolized in the liver to form VMA.
Step-by-step explanation:
The most common metabolite seen with pheochromocytoma is Vanillylmandelic acid (VMA). Pheochromocytoma is a tumor of the adrenal medulla that causes excessive production of catecholamines, such as dopamine, norepinephrine, and epinephrine. These catecholamines are metabolized in the liver by enzymes like Catechol-O-Methyl-Transferase (COMT) and Mono-Amine Oxidase (MAO), leading to the formation of VMA as a major excretory product.