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,…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 the release of 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 of blood vessels (increasing blood pressure) and adrenaline increases heart rate and metabolism. After completing their actions, the hormones are metabolised to form inactive compounds (metabolites). Dopamine becomes 3-methoxytyramine (3-MT) and homovanillic acid (HVA), noradrenaline changes to normetanephrine and hydroxymethylmandelic acid (HMMA) (also called vanillylmandelic acid (VMA)), and adrenaline becomes metanephrine and HMMA. Both the hormones and their 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 80-85% of phaeochromocytomas are found in the adrenal glands. A few are cancerous, however most are benign and 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 and catecholamine metabolite testing can be used to help detect the presence of phaeochromocytomas. Only 0.1-0.6% of cases of high blood pressure are due to phaeochromocytomas; but this is one of the few causes of high blood pressure that can be cured. So it is important to diagnose and treat these rare tumours. In most cases, the tumours can be surgically removed and/or treated to reduce the amount of catecholamines being produced thus reducing or removing symptoms and complications. Catecholamine testing measures the amount of adrenaline, noradrenaline, and dopamine in the plasma or urine. Increasingly laboratories are measuring the catecholamine metabolites, metadrenaline and normetadrenaline in urine or plasma as well, as recent evidence suggests they are more reliable tests because they are continually produced by the tumour. 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. How is the sample collected for testing?For the 24-hour urine collection, all of your urine should be saved for a 24-hour period into a bottle containing a small amount of acid. This helps preserve the urine sample. It is important that the sample is stored somewhere cool during this period, and that you return the bottle as soon as possible. You must write down the time and date that you started and finished the collection on either the collection bottle or the laboratory request form. Blood catecholamines are collected by putting a needle into a vein in your arm. Is any test preparation needed to ensure the quality of the sample?For a blood sample for catecholamines you may be asked to lie down and rest quietly for 15-30 minutes prior to sample collection, and your blood may be collected while you are lying down. In other circumstances, you may just be seated upright with little or no rest time before the sample collection. See MoreSee Less
