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  • Title: Dietary influences on plasma and urinary metanephrines: implications for diagnosis of catecholamine-producing tumors.
    Author: de Jong WH, Eisenhofer G, Post WJ, Muskiet FA, de Vries EG, Kema IP.
    Journal: J Clin Endocrinol Metab; 2009 Aug; 94(8):2841-9. PubMed ID: 19567530.
    Abstract:
    CONTEXT: Measurements of the 3-O-methylated metabolites of catecholamines [metanephrines (MNs)] in plasma or urine are recommended for diagnosis of pheochromocytoma. It is unclear whether these tests are susceptible to dietary influences. OBJECTIVE: The aim of the study was to determine the short-term influence of a catecholamine-rich diet on plasma and urinary fractionated MNs. DESIGN, SETTING, AND PARTICIPANTS: We conducted a crossover study in a specialist medical center involving 26 healthy adults. INTERVENTIONS: Subjects consumed catecholamine-rich nuts and fruits at fixed times on one day (about 35 mumol dopamine and 1 mumol norepinephrine) and catecholamine-poor products on another day. Blood and urine samples were collected at timed intervals before, during, and after experimental and control interventions. MAIN OUTCOME MEASURES: Isotope-dilution mass spectrometry-based measurements of plasma and urinary concentrations of free and deconjugated 3-methoxytyramine (3-MT), normetanephrine (NMN), and MN were made. RESULTS: The catecholamine-rich diet had substantial effects (up to 3-fold increases) on plasma concentrations and urinary outputs of free and deconjugated 3-MT. Dietary catecholamines had negligible influences on free NMN in plasma and urine, but substantial effects (up to 2-fold increases) on deconjugated NMN in plasma and urine. Concentrations of free and deconjugated MN in plasma and urine remained unaffected. CONCLUSIONS: Dietary restrictions should be considered to minimize false-positive results for urinary and plasma deconjugated MNs during diagnosis of pheochromocytoma. Similar considerations appear warranted for plasma and urinary free 3-MT, but not for free NMN or MN, indicating advantages of measurements of the free compared to deconjugated metabolites.
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