Metanephrine is a metabolite of epinephrine (adrenaline), which is a blood-regulating hormone (called a catecholamine) released during times of physical or emotional stress, and
when found in excess (for long periods) a marker for metanephrine-secreting tumors (Pheochromocytoma and Paraganglioma) and also tested during treatments of
confirmed tumors and to monitor any recurrence.