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What is Best for diagnosing pheochromocytoma is:September 2008 and explain in detail?
Ans. A: Urinary catecholamines and their metabolitesThe diagnosis of pheochromocytoma is established by the demonstration of elevated 24-hour urinary excretion of free catecholamines (norepinephrine and epinephrine) or catecholamine metabolites (vanillylmandelic acid and total metanephrines).The measurement of plasma catecholamines can also be of value in the diagnosis of pheochromocytoma.However, the measurement of plasma catecholamines has limited sensitivity and specificity. Plasma metanephrines have been repoed to be more sensitive than plasma catecholamines. Pharmacologic testing with agents such as glucagon or clonidine is rarely required to make the diagnosis