Methoxytyramine, one of the O-methylated metabolites of catecholamines, was used to discriminate different hereditary forms of pheochromocytoma, which indicated that patients with MEN2 and NF1 genes presented with tumors characterized by increased plasma concentrations of metanephrine [36,37]. Here, NF1 is linked to hereditary pheochromocytoma-paraganglioma.