Normetanephrine, Plasma Unit Converter

Normetanephrine is a metabolite of norepinephrine, one of the body's main stress hormones. It is produced when the enzyme catechol-O-methyltransferase (COMT) breaks down norepinephrine.

Plasma free normetanephrine measures the unbound form of this metabolite circulating in your blood. Because normetanephrine is produced continuously within catecholamine-producing cells, it provides a more stable and reliable marker of norepinephrine activity than measuring norepinephrine itself, which fluctuates rapidly.

This test is most commonly used to help diagnose or rule out pheochromocytoma and paraganglioma, rare tumors that overproduce catecholamines. It is typically ordered as part of a fractionated plasma free metanephrines panel alongside metanephrine.

About 60% of plasma normetanephrine comes from the metabolism of norepinephrine released by sympathetic nerves throughout the body. Roughly 25% is produced within the adrenal medulla, and the remaining 15% comes from other catecholamine-producing (chromaffin) cells.