Catecholamines

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.

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.

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.

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.

No, they can be detected and removed but not prevented. In most cases, the tumor is benign and, once it is removed, it will not recur.