Dopamine and dopa urinary excretion in patients with pheochromocytoma--diagnostic implications

Pheochromocytoma, a potentially life-threatening disease, is a rare cause of hypertension. Most pheochromocytomas secrete excessive amounts of noradrenaline and adrenaline. It has been suggested by some authors that high circulating levels of dopamine and the catecholamine precursor dihydroxyphenylalanine (dopa) are more often associated with malignant rather than benign pheochromocytomas. Therefore the aim of this study was to evaluate urinary excretion of dopamine and dopa in patients with pheochromocytoma and to determine their role as a potential marker for malignancy of the tumour. We retrospectively analysed 120 consecutive patients (mean age 41 +/- 12 years) with histopathologically confirmed pheochromocytomas. All subjects were divided as follows: group 1 included patients with both elevated and normal dopamine urinary excretion; group 2 was characterized by increased and normal dopa urinary excretion. Dopamine urinary excretion was increased in all patients with malignant pheochromocytoma, but higher levels were also observed in some patients with a benign tumour included in group 1. Urinary excretion of dopa was in the normal range in all subjects with malignant pheochromocytoma. The results indicate that in some pheochromocytoma patients excessive dopamine excretion may point to malignant tumour, but is not a discriminating marker for malignancy in the whole studied group.