Epinephrine (adrenaline), norepinephrine (noradrenaline) and dopamine are neurotransmitters (molecules that allow the transfer of nerve influx) of the catecholamine group controlling, among other things, blood pressure in response to stress. They are produced in the central part of the two adrenal glands and elsewhere in the nervous system. A rare adrenal medulla gland tumour (pheochromocytoma) and an even rarer nervous system tumour (paraganglioma) can be responsible for the secretion of very high amounts of catecholamines accompanied by sudden and severe bursts of hypertension. Since these bursts of hypertension vary over time, it is sometimes difficult to confirm the diagnosis with a blood test. The measurement of catecholamines and their inactive metabolites (metanephrine, normetanephrine, VMA and HVA) in 24-hour urine samples increases the likelihood of detecting these tumours.
A normal result in the different catecholamines and their metabolites can not rule out the possibility of a pheochromocytoma if there was no hypertension surge during the collection period. The urine collection often needs to be repeated. Slightly high results may come from other causes such as episodes of stress, smoking, caffeine and several medications. The higher the results, the larger the tumour (generally benign) should be.