Rudi Hayden

Urologist

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Blood-tests Explained


Disclaimer:

This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion

Catecholamines


At a Glance

Why Get Tested?

To help confirm or rule out a rare adrenal tumor called a pheochromocytoma or a rare extra-adrenal tumor called a paraganglioma; these tumors produce excess hormones called catecholamines, which are broken down to metanephrines.

When to Get Tested?

After or in conjunction with plasma free metanephrines and/or urine metanephrines tests and when your healthcare provider needs additional information regarding a possible catecholamine-secreting tumor

Sample Required?

A 24-hour urine sample; sometimes a blood sample drawn from a vein in your arm

Test Preparation Needed?

These tests are affected by certain drugs, foods, and stresses. Inform your healthcare provider of 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 provider or the collection site will instruct you as to their specific requirements.

The Test Sample

What is being tested?

Thumbnail diagram of the adrenal gland

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.

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.

The Test

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 in symptomatic people. It also may be ordered when a tumor is treated or removed to monitor for recurrence.

Catecholamines are a group of similar hormones that are released into the bloodstream in response to physical or emotional stress. The primary catecholamines are dopamine, epinephrine (adrenaline), and norepinephrine. These hormones are broken down to their metabolites metanephrine, normetanephrine, homovanillic acid, and vanillylmandelic acid. (See the "What is being tested?" section for more on this.) Pheochromocytomas and paragangliomas produce these hormones 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 evaluate an individual for 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.

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.

The catecholamine blood test may be useful when the person has persistent hypertension or is 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.

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 a person has only moderately elevated levels, then the healthcare provider may re-evaluate the person's medications, diet, and stress level to look for interfering substances or conditions. Once these are resolved, the person may then be tested again to determine whether the levels are still elevated and take appropriate action.

When is it ordered?

Catecholamines testing may be ordered when tests for plasma free metanephrines and/or urine metanephrines are inconclusive and a health practitioner needs more information about a possible catecholamine-secreting tumor. It may be ordered when a person, especially a relatively young person (younger than age 40) has sudden bursts (paroxysms) of signs and symptoms such as:

  • High blood pressure (hypertension), especially when a person has hypertension that is not responding to treatment, as people with pheochromocytomas and paragangliomas are frequently resistant to conventional therapies
  • Severe headaches
  • Sweating
  • Flushing
  • Rapid heart rate (palpitations)
  • Tremor

The tests may also be ordered for an asymptomatic person if an adrenal or neuroendocrine tumor is detected during a scan conducted for another purpose or if the person has a strong personal or family history of pheochromocytoma.

It may also be ordered at intervals when a person has 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 in a person with signs and symptoms strongly suggests the presence of a catecholamine-secreting tumor. It indicates that further investigation is needed. It is recommended that imaging studies be performed to locate the catecholamine-secreting tumor once there is clear biochemical evidence of such a tumor.

If catecholamine levels are elevated in a person who has been treated for a catecholamine-secreting tumor, then it is likely that either treatment was not fully effective or that the tumor is recurring and appropriate follow up is needed.

If the level of catecholamines is normal, then it is unlikely that a person has a catecholamine-secreting tumor. However, pheochromocytomas do not necessarily produce catecholamines at a constant rate. Therefore, if the person has not had a recent episode of hypertension, their blood and urine concentrations of catecholamines 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 catecholamine-secreting tumors, 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 extra-adrenal 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.)

It has been proposed that all patients diagnosed with a pheochromocytoma or extra-adrenal paraganglioma should consider genetic counseling and testing. Early identification of a hereditary syndrome allows for early screening for other associated tumors. In addition, some patients with a hereditary syndrome are more likely to develop malignant or recurrent disease. Knowledge of the specific genetic mutation permits increased vigilance during preoperative localization or postoperative surveillance of such patients.

It is also recommended that if a mutation is identified, predictive genetic testing should be offered to asymptomatic at-risk family members.

A variety of medications can interfere with catecholamines testing. However, it is important to talk to your healthcare provider before discontinuing any prescribed medications. Your healthcare provider 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.

Tests used for determining the presence of catecholamine-secreting tumors (pheochromocytomas and paragangliomas) include plasma catecholamines, urine catecholamines, plasma free metanephrines and urine metanephrines. These tests measure either the catecholamines or their metabolites (metanephrines) and have varying sensitivity and specificity. Current guidelines recommend plasma free metanephrines or urinary fractionated metanephrines for initial biochemical testing. The healthcare provider may, however, select any one (or more than one) depending on the person's presentation, family history, and/or genetic profile.