At a Glance
Why Get Tested?
When to Get Tested?
If you have symptoms of persistent or episodic high blood pressure such as severe headaches, rapid heart rate and sweating
A 24-hour urine sample or possibly a blood sample drawn from a vein in the arm
Test Preparation Needed?
These tests are affected by certain drugs, foods and stresses. Inform your doctor of any medications you are taking and follow any instructions you are given for things to avoid before sample collection.
The Test Sample
What is being tested?
Catecholamines are a group of similar hormones produced in the 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 (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 glucose and fatty acid release (for energy), dilate bronchioles (small air passages in the lungs) and dilate the pupils. Noradrenaline also constricts 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 homovanillic acid (HVA), noradrenaline breaks down into normetanephrine and hydroxymethylmandelic acid (HMMA) (vanillylmandelic acid (VMA)), and adrenaline becomes metanephrine and HMMA. Both the hormones and their metabolites are excreted in the urine.
Normally, catecholamines and their metabolites are present in the body in small, fluctuating amounts that only increase appreciably during and shortly after a bout of stress. 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. This can cause persistent hypertension (high blood pressure) and/or bouts or episodes of severe hypertension, resulting in symptoms such as severe headaches, palpitations, sweating, nausea, anxiety and tingling in the extremities.
About 90% of phaeochromocytomas are located in the adrenal glands. While a few are cancerous, most are benign - they 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 that the phaeochromocytoma causes may damage body organs, such as the kidneys and heart, and raise the risk of an affected patient having 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 hypertension. In most cases, the tumours can be surgically removed and/or treated to significantly reduce the amount of catecholamines being produced and to reduce or eliminate their associated symptoms and complications.
Catecholamine testing measures the amount of adrenaline, noradrenaline and dopamine in the plasma or urine. (The metabolites of these hormones may be measured separately with a urine metanephrine and/or 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.
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. It is important that the sample be refrigerated during this time period.
Plasma catecholamines are collected by inserting a needle into a vein in your arm.
Is any test preparation needed to ensure the quality of the sample?
There is some disagreement over the specifics of how the sample should be collected. 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.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.