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The Test Sample
What is being tested?
Catecholamines are a group of similar hormones released into the bloodstream in response to physical or emotional stress. The primary catecholamines are dopamine, epinephrine (adrenaline), and norepinephrine. Catecholamine testing measures the amounts of these hormones in the urine and/or blood. Urine testing is recommended over blood testing. Just the stress of having blood drawn can increase catecholamine blood levels, so results from blood tests are not as reliable as results from urine tests.
Catecholamines are produced in the adrenal medulla, the interior portion of the adrenal glands, and released into the blood. The adrenal glands are small, triangular organs located on top of each kidney. Catecholamines are also produced by cells of the sympathetic nervous system. They are released into the bloodstream in response to physical and emotional stress. They help transmit nerve impulses in the brain, increase glucose and fatty acid release for energy, dilate bronchioles, and dilate the pupils. Norepinephrine also constricts blood vessels, causing increased blood pressure, and epinephrine increases heart rate and metabolism.
After completing their actions, catecholamines are metabolized to inactive compounds. Dopamine becomes homovanillic acid (HVA), norepinephrine breaks down into normetanephrine and vanillylmandelic acid (VMA), and epinephrine becomes metanephrine and VMA. Both the hormones and their metabolites are eliminated from the body 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 stressful situation. However, rare tumors called pheochromocytomas and paragangliomas can produce large amounts of the hormones, resulting in increased concentrations in both the blood and urine. This can cause persistent or sudden bursts of hypertension, which may lead to severe headaches. Other symptoms include heart palpitations, sweating, nausea, anxiety, and tingling in the hands and feet.
Pheochromocytomas and paragangliomas are rare. While a few are cancerous, most are benign and do not spread beyond their original location. Left untreated, however, these tumors may continue to grow and symptoms may worsen. Over time, the hypertension caused by the excess hormones may lead to kidney damage, heart disease, and raise the risk for stroke or heart attack.
The Endocrine Society recommends that a test for plasma free metanephrine or urine metanephrine be used to help detect the presence of pheochromocytomas and paragangliomas (catecholamine-secreting tumors). Urine and/or blood tests for catecholamines may be used to help confirm or rule out the presence of these tumors. However, blood tests are not as reliable as urine testing because the stress from having blood drawn can elevate catecholamines.
It is important to diagnose and treat these tumors because they cause a potentially curable form of hypertension. In most cases, the tumors 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.
How is the sample collected for testing?
For the urine test, a 24-hour urine collection is needed. All urine is saved for a 24-hour period. It is important that the sample be refrigerated during this time period. A preservative is required and is usually provided with the collection device.
Blood for catecholamine testing is collected by inserting a needle into a vein in the arm. Although the patient may be seated for the collection, it is recommended that the patient be lying down. The healthcare provider or the collection site will instruct the patient as to their specific requirements.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
Catecholamine levels are affected by certain drugs, foods, and stresses. Preparation for the test is important to ensure that an appropriate sample is collected and for correct interpretation of results. Follow any instructions given by the healthcare provider or the collection site or laboratory.
- People being tested should talk to their healthcare provider about prescription medications and over-the-counter drugs and supplements that they are taking. It may be necessary to discontinue medications for some time prior to the test. However, the patient should not stop taking any medications without consulting their healthcare provider.
- The person being tested will also be instructed on what foods to avoid. Fasting may also be required prior to the blood sample being drawn.
- Emotional and physical stresses and vigorous exercise should be minimized prior to and during sample collection as they can increase catecholamine release.