These tests are affected by certain drugs, foods, and stresses. Tell your healthcare practitioner about any medications you are taking and follow any preparation instructions you are given before sample collection. Although you may be seated for collection of the blood sample, it is recommended that you be lying down. Your healthcare practitioner or the collection site will instruct you as to their specific requirements.
Catecholamines are a group of similar substances released into the blood 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 blood 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 (collectively called PPGL) 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.
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. A preservative is required and is usually provided with the collection container.
Blood for catecholamine testing is collected by inserting a needle into a vein. Although you may be seated for the collection, it is recommended that you be lying down. The healthcare practitioner or the collection site will instruct you as to their specific requirements.
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 practitioner or the collection site or laboratory.
- You should talk to your healthcare provider about prescription medications and over-the-counter drugs and supplements you are taking. It may be necessary to discontinue medications for some time prior to the test.
- However, you should not stop taking any medications without consulting your healthcare practitioner. Your healthcare practitioner will work with you to identify potentially interfering substances and drug treatments and to determine which of them can be safely interrupted and which must be continued for your well-being.
- You will also be instructed on what foods to avoid. Fasting may also be required prior to the blood sample collection.
- Avoid emotional and physical stresses and vigorous exercise prior to and during sample collection as they can increase catecholamine release.
How is it used?
Catecholamines testing may be used in follow up to plasma free metanephrines and/or urine metanephrines testing to help confirm or rule out rare tumors called pheochromocytomas and paragangliomas. It also may be used to monitor for recurrence of these tumors. Pheochromocytomas and paragangliomas produce catecholamines in excess, so measuring the amount in the blood and/or urine may help detect the tumor.
The Endocrine Society recommends tests for plasma free metanephrines and urine metanephrines to help diagnose pheochromocytomas or paragangliomas. If results of those tests are inconclusive, then urine testing for catecholamines may be used to provide additional information. Blood catecholamine testing may sometimes be used, but it is not as reliable because the stress of having blood drawn can increase levels. However, your healthcare practitioner may select any one (or more than one) of these tests depending on your signs and symptoms, family history, and/or genetic profile.
- Urine catecholamines testing measures the total amount of catecholamines released into the urine in 24 hours. Since the hormone levels may fluctuate significantly during this period, the urine test may detect excess episodic production that is missed with the blood test.
- Catecholamine blood test may be useful when you have persistent hypertension or are currently experiencing a sudden burst (paroxysm) of hypertension. This is because the hormones do not stay long in the blood; they are used by the body and rapidly broken down (metabolized) and/or then eliminated.
When is it ordered?
Catecholamines testing may be ordered when tests for plasma free metanephrines and/or urine metanephrines are inconclusive and a healthcare practitioner needs more information about a possible tumor that produces catecholamines. It may be ordered when you have sudden bursts (paroxysms) of specific signs and symptoms (especially If you are younger than age 40). Signs and symptoms may include:
- High blood pressure (hypertension), especially when you have hypertension that is not responding to treatment (people with PPGL are frequently resistant to conventional therapies)
- Severe headaches
- Rapid heart rate (palpitations)
It may also be ordered at intervals when you have been previously treated for one of these tumors.
What does the test result mean?
A high level of catecholamines in the blood and/or urine when you have signs and symptoms strongly suggests the presence of a tumor that produces catecholamines. It indicates that further investigation is needed. It is recommended that imaging studies be performed to locate the tumor once test results show clear evidence of such a tumor.
The test for catecholamines is very sensitive and false positives do occur. The test is affected by stress, drugs, smoking, and various foods such as caffeine-containing drinks and alcohol. If you have only moderately elevated levels, then your healthcare practitioner may re-evaluate your medications, diet, and stress level to look for interfering substances or conditions. Once these are resolved, you may then be tested again to determine whether the levels are still elevated and take appropriate action.
If catecholamine levels are elevated after you have been treated for such a tumor, then it is likely that either treatment was not fully effective or the tumor has returned and appropriate follow up is needed.
If the level of catecholamines is normal, then it is unlikely that you have a tumor that produces catecholamines. However, pheochromocytomas do not necessarily produce catecholamines at a constant rate. Therefore, if you have not had a recent episode of hypertension, your blood and urine catecholamine levels could be at normal or near normal levels even when a pheochromocytoma is present. If suspicion remains high, testing may be repeated.
Is there anything else I should know?
While plasma and urine catecholamines tests can help detect and diagnose tumors that produce catecholamines, they cannot tell the location of the tumor, whether there is more than one, or whether or not the tumor is benign (although most are). The total amount of catecholamines produced will tend to increase as the tumor increases in size or number.
Although pheochromocytomas and paragangliomas are rare, 25% occur in the setting of a hereditary syndrome associated with alterations in specific genes. These genetic syndromes have thus been identified as carrying an increased tumor risk. Examples include MEN-1 and MEN-2 (Multiple Endocrine Neoplasia, types 1 and 2) syndromes. (For more information on these, see Genetics Home Reference: Multiple endocrine neoplasia.)
Is there any way to prevent a pheochromocytoma from forming?
Is it really necessary to collect urine for 24 hours?
Yes, for accurate test results it is essential that all of the urine be collected. Catecholamines are released in varying amounts at varying times, so the one sample not included might be the one with the most hormones in it. For general instructions, read about the 24-hour urine collection.
Can my state of mind really affect my test results?