Epinephrine and norepinephrine are metabolized to metanephrine and normetanephrine. Measurement of total metanephrines in the urine is a good screen for pheochromocytoma. Measurement of creatinine output on the same sample allows determination of the metanephrine-to-creatinine ratio. This is a simple and sensitive test for pheochromocytoma, but false positive results can limit the specificity.
