Catecholamines, Plasma and Urine
At a Glance
Why Get Tested?
To help diagnose or rule out a pheochromocytoma or other neuroendocrine tumor
When to Get Tested?
When you have symptoms of increased catecholamine release, such as persistent or episodic high blood pressure, severe headaches, rapid heart rate, and sweating
Sample Required?
A blood sample drawn from a vein in the arm or a 24-hour urine sample
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 adrenal medulla, the interior portion of the adrenal glands. Adrenal glands are small, triangular organs located on top of each kidney. The primary catecholamines are dopamine, epinephrine (adrenaline), and 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, and dilate the pupils. Norepinephrine also constricts blood vessels, increasing blood pressure, and epinephrine increases heart rate and metabolism. After completing their actions, the hormones 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 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. Pheochromocytomas and other neuroendocrine tumors, 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 or episodic bouts of hypertension, which may lead to severe headaches. Other symptoms of catecholamine release include palpitations, sweating, nausea, anxiety, and tingling in the extremities.
About 90% of pheochromocytomas are located in the adrenal glands. While a few are cancerous, most are benign and they do not spread beyond their original location, although they may continue to grow. Left untreated, the symptoms may worsen as the tumor grows and, over a period of time, the hypertension that the pheochromocytoma causes may damage 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 pheochromocytomas. Although only about 800 cases a year are diagnosed in the U.S. according to the National Cancer Institute, it is important to diagnose and treat these rare 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.
Catecholamine testing measures the amounts of epinephrine, norepinephrine, and dopamine in the plasma or urine. The plasma test measures the amount of hormone present in the blood 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. Although 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.
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?
Both plasma and urine catecholamines are affected by certain drugs, foods, and stresses. Inform your doctor of any medications you are taking and follow any instructions you are given to ensure that an appropriate sample is collected.
The Test
How is it used?
Catecholamine testing is primarily used to help detect and rule out pheochromocytomas in symptomatic patients. It also may be ordered to help monitor the effectiveness of treatment when a pheochromocytoma is discovered and removed and to monitor for recurrence. The plasma test is most useful when the patient has persistent hypertension or is currently experiencing an episode of hypertension. This is because the hormones do not linger in the blood; they are used by the body, metabolized, and/or excreted. Urine catecholamine testing measures the total amount of catecholamines released in 24 hours. Since the hormone levels may fluctuate significantly during this period, the urine test may detect excess production that is missed with the blood test. Plasma and urine tests may be ordered together or separately to look for excessive amounts of both catecholamines and their metabolites.
Since these tests are affected by drugs, foods, and stresses, there will be a certain number of false positives. For this reason, catecholamine testing is not recommended as a screen for the general public. Doctors will frequently investigate a positive result by evaluating a patient’s stresses and intake, work to alter or minimize any influences, and then repeat the test to confirm the original findings.
Occasionally, the tests may be ordered on an asymptomatic person if an adrenal or neuroendocrine tumor is detected during a scan that is done for another purpose or if the patient has a strong personal or family history of pheochromocytoma.
When is it ordered?
Catecholamine testing is ordered when a doctor either suspects that a patient has a pheochromocytoma or wants to rule out the possibility. He may order it when a patient has persistent or recurring hypertension along with symptoms such as headaches, sweating, flushing, and rapid heart rate. It may also be ordered when a patient has hypertension that is not responding to treatment as patients with pheochromocytomas are frequently resistant to conventional therapies.
Occasionally, the test may be ordered when an adrenal tumor is detected incidentally or when a patient has a family history of pheochromocytomas. It may also be used as a monitoring tool when a patient has been treated for a previous pheochromocytoma.
What does the test result mean?
Since the catecholamine test is sensitive to many outside influences and pheochromocytomas are rare, a doctor may see more false positives with this test than true positives. If a symptomatic patient has large amounts of catecholamines in her blood and/or urine, further investigation is indicated. Serious illnesses and stresses can cause moderate to large temporary increases in catecholamine levels. Doctors must evaluate the patient as a whole - her physical condition, emotional state, medications, and diet. When interfering substances and/or conditions are found and resolved, the doctor will frequently re-test the patient to determine whether the catecholamines are still elevated. The doctor may also order blood and/or urine metanephrine testing to help confirm his findings and imaging tests, such as an MRI, to help find the tumor(s).
If levels are elevated in a patient who has had a previous pheochromocytoma, then it is likely that either treatment was not fully effective or that the tumor is recurring.
If the concentrations of catecholamines are normal in both the plasma and urine, then it is unlikely that a patient has a pheochromocytoma. Pheochromocytomas do not necessarily produce catecholamines at a constant rate, however. If the patient has not had a recent paroxysm of hypertension, their plasma and urine concentrations of catecholamines could be at normal or near normal levels even when a pheochromocytoma is present.
Is there anything else I should know?
While plasma and urine catecholamine testing can help detect and diagnose pheochromocytomas, they cannot tell the doctor where the tumor is, whether there is more than one, or whether or not the tumor is benign (although most are). The amount of catecholamines produced does not necessarily correspond to the size of the tumor. This is a physical characteristic of the tumor tissue. The total amount of catecholamines produced will tend to increase, however, as the tumor increases in size.
A variety of medications can interfere with catecholamine testing. However, it is very important to talk to your doctor before discontinuing any prescribed medications. He will work with you to identify interfering substances and drug treatments to determine which of them can be safely interrupted and which must be continued for your well-being. Some of the substances that can interfere with catecholamine testing include: acetaminophen, aminophylline, amphetamines, appetite suppressants, coffee, tea, and other forms of caffeine, chloral hydrate, clonidine, dexamethasone, diuretics, epinephrine, ethanol (alcohol), insulin, imipramine, lithium, methyldopa (Aldomet), MAO (monoamine oxidase) inhibitors, nicotine, nitroglycerine, nose drops, propafenone (Rythmol), reserpine, salicylates, theophylline, tetracycline, tricyclic antidepressants, and vasodilators. The effects of these drugs on catecholamine results will be different from patient to patient and are often not predictable.
Common Questions
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Article Sources
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.
Sources Used in Current Review
Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby’s Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 987-990.
Wu, A. (2006). Tietz Clinical Guide to Laboratory Tests, Fourth Edition. Saunders Elsevier, St. Louis, Missouri. Pp 226-230.
Pacak, K. et. al. (2007 March 21). Pheochromocytoma: Recommendations for Clinical Practice from the First International Symposium. Medscape from Nature Clinical Practice Endocrinology & Metabolism [On-line information]. Available online at http://www.medscape.com/viewarticle/553428 through http://www.medscape.com. Accessed on 8-24-08.
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Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber’s Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby’s Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Martell, B. Updated (2003 May 20, Updated). Catecholamines – blood. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003561.htm.
Webner, D. Updated (2003 August 18, Updated). Catecholamines – urine. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/003613.htm.
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