Catecholamines, plasma and urine

Catecholamines are a group of similar hormones produced in the medulla (central portion) of the adrenal glands. The adrenal glands are small, triangular organs which sit on top of each kidney. The main catecholamines are dopamine, adrenaline (epinephrine), and noradrenaline (norepinephrine). These hormones are released into the bloodstream in response to physical or emotional stress. They help transmit nerve impulses in the brain, increase release glucose and fatty acid into the blood (for energy), widen the small air passages in the lungs, and widen (dilate) the pupils of the eye. Noradrenaline also reduces the size blood vessels (increasing blood pressure) and adrenaline increases heart rate and metabolism.

After completing their actions, the hormones are metabolised to form inactive compounds. Dopamine becomes 3-methoxytyramine and homovanillic acid (HVA), noradrenaline changes to normetanephrine and hydroxymethylmandelic acid (HMMA) (vanillylmandelic acid (VMA)), and adrenaline becomes metanephrine and HMMA. Both the hormones and their breakdown products (metabolites) are removed in the urine.

Normally, catecholamines and their metabolites are present in the body in small, varying amounts that only increase greatly during and shortly after a period of stress. Phaeochromocytomas and other neuroendocrine tumours, however, can produce large amounts of catecholamines, resulting in greatly increased levels of the hormones and their metabolites in both the blood and urine. This can cause persistent high blood pressure and/or bouts or episodes of very high blood pressure, resulting in severe headaches, palpitations, sweating, sickness, anxiety, and tingling in the fingers and toes.

About 90% of phaeochromocytomas are found in the adrenal glands. While a few are cancerous, most are benign meaning that they do not spread beyond their original location, although most do continue to grow. Left untreated, the symptoms may get worse as the tumour grows and, over a period of time, the high blood pressure that the phaeochromocytoma causes may damage body organs, such as the kidneys and heart, and increase the risk of a stroke or heart attack.

Urine and plasma catecholamine testing can be used to help detect the presence of phaeochromocytomas. It is important to diagnose and treat these rare tumours because they cause a potentially curable form of high blood pressure. In most cases, the tumours can be surgically removed and/or treated to reduce the amount of catecholamines being produced and to reduce or remove symptoms and complications.

Catecholamine testing measures the amount of adrenaline, noradrenaline, and dopamine in the plasma or urine. The metabolites of these hormones can also be measured separately as urine or plasma metanephrines and/or a urine HMMA test). The plasma catecholamine test measures the amount of hormones present at the moment of collection, while the urine test measures the amount excreted over a 24-hour period.

For the 24-hour urine collection, all of your urine should be saved for a 24-hour period. It is important that the sample be stored cool in a refrigerator during this period.
Blood catecholamines are collected by putting a needle into a vein in your arm.