Metanephrines, Total, Plasma Unit Converter

Total plasma metanephrines is a blood test that measures the combined levels of two catecholamine metabolites: metanephrine (from epinephrine) and normetanephrine (from norepinephrine).

Catecholamines are "fight or flight" hormones produced by the adrenal glands and sympathetic nervous system. The enzyme COMT (catechol-O-methyltransferase) continuously converts epinephrine into metanephrine and norepinephrine into normetanephrine. The total value represents the sum of these two metabolites.

This test is primarily used to screen for pheochromocytoma and paraganglioma, rare tumors that produce excess catecholamines. Because metanephrines are produced continuously (not just during bursts of hormone release), they provide a more stable and reliable signal than measuring catecholamines directly.

Metanephrine is produced mainly in the adrenal medulla, where COMT continuously converts stored epinephrine. Normetanephrine comes from both the adrenal medulla and from norepinephrine released at sympathetic nerve endings throughout the body.