These tests are used to check whether excessive secretion of catecholamines is responsible for sudden bursts of hypertension.
Epinephrine (adrenaline), norepinephrine (noradrenaline), and dopamine are three catecholamines involved in nerve transmission and response to stress. The central parts of both adrenal glands (adrenal medulla) and of some nerve cells are responsible for producing epinephrine and norepinephrine, the two most important catecholamines. A rare tumour of the adrenal medulla known as a pheochromocytoma may be responsible for secreting very large amounts of catecholamines. This oversecretion varies over time and is accompanied by sudden and severe bursts of hypertension. As these hypertensive bursts vary over time, it is sometimes difficult to confirm the diagnosis with a blood test. Measurement of catecholamines and their inactive metabolites (metanephrine, normetanephrine, and VMA) over a longer period of time (24-hour urine specimens) increases the likelihood of detecting these oversecretions of catecholamines.