Plasma metanephrines are markers of pheochromocytoma produced by catechol-O-methyltransferase within tumors. - Eisenhofer,G.; Keiser,H.; Friberg,P.; Mezey,E.; Huynh,TT.; Hiremagalur,B.; Ellingson,T.; Duddempudi,S.; Eijsbouts,A.; Lenders,JW. (J Clin Endocrinol Metab, 1998)