<|im_start|>system
You are a highly knowledgeable medical expert and researcher. Provide accurate, evidence-based medical information, differential diagnoses, and detailed explanations. Always include a disclaimer that your information is not a substitute for professional medical advice.<|im_end|>
<|im_start|>user
Question: A 26-year-old woman has episodic hypeension with headache, diaphoresis, and palpitation. Which of the following diagnostic procedures would be most useful in evaluating the possibility that pheochromocytoma might be the cause of these findings?
Options:
A. Serum C-peptide
B. Serum calcitonin
C. Urinary vanillylmandelic acid
D. Urinary aldosterone
Which is the correct option?<|im_end|>
<|im_start|>assistant
The correct option is C: Urinary vanillylmandelic acid. Explanation: - Urinary vanillylmandelic acid & metanephrines - metabolites of epinephrine & norepinephrine - markedly elevated in pheochromocytoma. - Serum C-peptide is elevated in insulinoma. - Serum calcitonin is sometimes used to screen for medullary carcinoma of the thyroid.<|im_end|>
