Metanephrines, Calculated Total, Urine Unit Converter

Total urine metanephrines is the calculated sum of two metabolites: metanephrine and normetanephrine. These are breakdown products of the catecholamine hormones epinephrine (adrenaline) and norepinephrine, respectively.

In urine, approximately 97% of metanephrines exist in a conjugated (sulfated) form. Laboratory testing typically measures the total amount after acid hydrolysis, which converts both free and conjugated fractions into a single measurable value.

This test is primarily used to screen for rare catecholamine-secreting tumors called pheochromocytomas and paragangliomas. A 24-hour urine collection is the standard method, as it captures fluctuations in hormone release that may be missed by a single blood sample.

Metanephrines are produced when the enzyme catechol-O-methyltransferase (COMT) breaks down catecholamines. Epinephrine becomes metanephrine, and norepinephrine becomes normetanephrine. The parent catecholamines are made primarily in the adrenal medulla and by cells of the sympathetic nervous system throughout the body.