3-Methoxytyramine (3-MT) is a metabolite of the neurotransmitter dopamine formed by the introduction of a methyl group to dopamine by the enzyme catechol-O-methyl transferase (COMT).
The measurement of 3-MT allows the detection of dopamine-producing tumours: For example a substantial number of patients with head-and-neck paragangliomas (HNPGL) have biochemically active tumors and only display increased excretion of 3-methoxytyramine, but not of other catecholamines or their metabolites.
The combined levels of free Metanephrine/Normetanephrine and free 3MT in plasma indicate a higher number of biochemically active HNPGLs than the 24-h urinary excretion rates of these markers.
LDN has developped an isotopic assay for the quantitative measurement of 3-MT. This is worldwide the first commercial assay for 3-MT.