Dietary influences on plasma and urinary metanephrines: implications for diagnosis of catecholamine-producing tumors.
BACKGROUND
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.


METHODS
We conducted a crossover study in a specialist medical center involving 26 healthy adults.


METHODS
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.


METHODS
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.
de Jong
Wilhelmina H A
WH
Department of Laboratory Medicine, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Eisenhofer
Graeme
G
Post
Wendy J
WJ
Muskiet
Frits A J
FA
de Vries
Elisabeth G E
EG
Kema
Ido P
IP
D000310:Adrenal Gland Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D004032:Diet; D004298:Dopamine / Q000031:analogs & derivatives / Q000097:blood / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008676:Metanephrine / Q000097:blood* / Q000652:urine*; D008875:Middle Aged; D009647:Normetanephrine / Q000097:blood / Q000652:urine; D010673:Pheochromocytoma / Q000097:blood / Q000175:diagnosis* / Q000652:urine
D009647:Normetanephrine; D008676:Metanephrine; C001746:3-methoxytyramine; D004298:Dopamine