Serum catecholamines are high. Serum metanephrines are normal.
My understanding is that
pheochromocytoma is normally screened by a 24 hour urine metanephrine, not a 24 hour urine catecholamines. That may have to do with the fragility of catecholamines, and metanephrines are used as a proxy because of their greater stability. If 24 hour urine metanephrines is high, then a 24 hour urine catecholamines can be done as confirmation. That seems to be clinical practice?
In this question, it was the premise about serum metanephrines being normal that throws me off. Does it make sense for serum catecholamines to be high and serum metanephrines to be normal, and does that fact alter the diagnostic pathway for the 24 hour urine? In other words, is it possible the 24 hour urines would mirror the results of the serum tests, with 24 hour urine catecholamines being high and 24 hour urine metanephrines being normal? If you started with the 24h metanephrines you might miss the 24h catecholamines result.