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A 50-year-old man consults a physician because he has been having transient periods of rapid heart beat accompanied by sweating, flushing, and a sense of impending doom. Physical examination is unrevealing, with no evidence of arrhythmia at the time of the exam. However, the man's wife is a nurse, so the physician asks that she take vital signs the next time one of the episodes occurs. She does, and demonstrates a blood pressure of 195/140 mm Hg with heart rate 160/min during the episode. She promptly takes her husband to the emergency room, but the spell is over by the time that he is seen. Urinary measurement of which of the following would most likely be diagnostic in this case?
A. Dehydroepiandrosterone (DHEA)
B. Human chorionic gonadotropin (hCG)
C. 17-ketosteroids
D. Vanillylmandelic acid VMA
E. Zinc protoporphyrin
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The correct answer is
D. This patient's history suggests pheochromocytoma. This rare (but often considered diagnostically) tumor is most often found in the adrenal medulla, although it can also be found in other tissues derived from neural crest cells. The tumor cells secrete catecholamine hormones or their precursors, which can cause either paroxysmal (as in this case) or persistent hypertension. Urinary metabolites of epinephrine and norepinephrine are vanillylmandelic acid (VMA) and homovanillic acid, so screening 24 hour urine collections for these substances can be helpful in establishing or excluding these diagnoses even in cases in which a physician does not observe one of the paroxysms and thus blood cannot be drawn for serum catecholamine levels at that time.
DHEA (choice A) is the adrenal androgen dehydroepiandrosterone (made by the adrenal cortex rather than the adrenal medulla), and is measured in serum in cases where adrenal virilism is suspected.
hCG (choice B) is human chorionic gonadotropin, and both serum and urine levels can increase in pregnancy or trophoblastic disease.
17-ketosteroids (choice C) are measured in urine during evaluation of congenital adrenal hyperplasia (a disorder of the adrenal cortex rather than medulla).
Zinc protoporphyrin (choice E) is measured in blood when evaluating possible porphyria.
