Context: The biochemical diagnosis of pheochromocytoma depends on the demonstration of elevated levels of catecholamines (i.e. epinephrine, norepinephrine, and dopamine) and their metabolites.
Objective: The aim of the study was to determine the preanalytical influence of a catecholamine-rich diet on urinary free and deconjugated catecholamines in healthy volunteers with a highly specific and sensitive analytical technique.
Design, setting, and participants: We conducted a crossover study involving 27 healthy adults in a specialist medical center.
Interventions: Subjects consumed catecholamine-rich nuts and fruits at fixed times on one day (about 35 micromol dopamine and 1 micromol norepinephrine) and catecholamine-poor products on another day. Urine samples were collected at timed intervals before, during, and after experimental and control interventions.
Main outcome measures: We performed automated online sample preparation coupled to isotope-dilution mass spectrometry measurements of urinary concentrations of free and deconjugated catecholamines.
Results: The catecholamine-rich diet had substantial effects on urinary excretions of deconjugated dopamine (up to 20-fold increases) and norepinephrine (up to 10-fold). Dietary catecholamines had less but significant effects on urinary excretion of free dopamine and norepinephrine (up to 1.5-fold increases). Outputs of urinary free and deconjugated epinephrine remained unaffected.
Conclusions: Urinary excretion of deconjugated norepinephrine and dopamine is strongly affected by consumption of catecholamine-rich food products, thereby increasing the likelihood of a false-positive test result during hormonal evaluation for pheochromocytoma. Measurement of deconjugated catecholamines should therefore preferably be avoided, in favor of measurement of urinary free catecholamines. In case of demonstrating increased urinary excretion of deconjugated norepinephrine and dopamine, repeated measurements are warranted with dietary restrictions prior to sample collection.