This test measures the amounts of metadrenaline and normetadrenaline that are excreted in the urine over a 24 hour period. Metadrenaline and normetadrenaline are the inactive metabolites of the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). Catecholamines are a group of similar hormones produced in the adrenal medulla (central portion) of the adrenal glands. The adrenal glands are small, triangular…This test measures the amounts of metadrenaline and normetadrenaline that are excreted in the urine over a 24 hour period. Metadrenaline and normetadrenaline are the inactive metabolites of the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). Catecholamines are a group of similar hormones produced in the adrenal medulla (central portion) of the adrenal glands. The adrenal glands are small, triangular organs located on top of each kidney. The primary catecholamines are dopamine, adrenaline, and noradrenaline. These hormones are released into the bloodstream in response to physical or emotional stress. They help transmit nerve impulses in the brain, increase glucose and fatty acid release for energy, dilate small air passages in the lungs called bronchioles, and dilate the pupils. Noradrenaline also constricts blood vessels, which increases blood pressure, and adrenaline increases heart rate and metabolism. After completing their actions, the catecholamines are metabolised to form inactive compounds (metabolites). Dopamine becomes 3-methoxytyramine (3-MT) and homovanillic acid (HVA), noradrenaline breaks down into normetadrenaline and vanillylmandelic acid (VMA) (also known as HMMA), and adrenaline becomes metadrenaline and VMA. Both the hormones and their metabolites are excreted in the urine. Urine metadrenaline testing measures the amount of both metadrenaline and normetadrenaline. These metabolites are usually present in the urine in small fluctuating amounts, that increase significantly during and shortly after the body is exposed to stress. Rare phaeochromocytomas and other neuroendocrine tumours, however, can produce large amounts of catecholamines, resulting in greatly increased concentrations of the hormones and their metabolites in both the blood and urine. The catecholamines that a phaeochromocytoma produces can cause persistent hypertension (high blood pressure) and episodes of severe hypertension. Phaeochromocytomas are responsible for high blood pressure in a very small proportion of individuals (approximately 0.1-0.6%). Other symptoms of excess catecholamines include headaches, palpitations, sweating, nausea, anxiety, and tingling in the extremities. About 80-85% of phaeochromocytomas are located 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 worsen as the tumour grows and, over a period of time, the hypertension from a phaeochromocytoma may cause kidney damage, heart disease, and raise the risk of a stroke or heart attack. Phaeochromocytomas that occur outside the adrenal glands are called paragangliomas. The urine metadrenaline test 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. How is the sample collected for testing? For the 24 hour urine collection, all urine should be collected into the container provided for a 24 hour period. It is important that the sample is stored somewhere cool during this period, and that you return the container 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. Please read and follow any instructions provided. Please ensure you collect urine for a complete 24 hour period, and that the urine container is labelled with your full name, date of birth, NHS/hospital number and the date/time that you started and finished the collection. Is any test preparation needed to ensure the quality of the sample? Foods such as coffee (including decaffeinated), tea, chocolate, vanilla, bananas, oranges and other citrus fruits should be avoided for several days prior to the test and during collection. There are also many medications that can potentially affect test results. People being tested should talk to their doctor about prescriptions and over-the-counter drugs and supplements that they are taking. Wherever possible, substances that are known to interfere should be discontinued prior to and during sample collection. However, it is important to consult with the doctor before stopping any medications. Emotional and physical stresses and vigorous exercise should be minimised prior to and during sample collection as they can increase catecholamine secretion. See MoreSee Less
