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This version published online on June 30, 2009
Journal of Clinical Endocrinology & Metabolism , doi:10.1210/jc.2009-0303
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Submitted on February 9, 2009
Accepted on May 7, 2009

Dietary Influences on Plasma and Urinary Metanephrines: Implications for Diagnosis of Catecholamine-Producing Tumors

Wilhelmina H.A. de Jong, Graeme Eisenhofer, Wendy J. Post, Frits A.J. Muskiet, Elisabeth G.E. de Vries, and Ido P. Kema*

Departments of Laboratory Medicine, Epidemiology, Medical Oncology, University Medical Center, Groningen, University of Groningen, The Netherlands; Institute of Clinical Chemistry and Laboratory Medicine and Department of Medicine, University of Dresden, Dresden, Germany

* To whom correspondence should be addressed. E-mail: i.p.kema{at}lc.umcg.nl.

Context: Measurements of the 3-O-methylated metabolites of catecholamines (metanephrines) in plasma or urine are recommended for diagnosis of pheochromocytoma. It is unclear whether these tests are susceptible to dietary influences.

Objective: To determine the short-term influence of a catecholamine-rich diet on plasma and urinary fractionated metanephrines.

Design, setting and participants: Cross-over 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 µmol dopamine and 1 µmol 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 metanephrine (MN).

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 metanephrines 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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