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. Catecholamine testing measures the amounts of these hormones in the blood and/or urine.
Catecholamines 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 stressful situation. 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 periods of hypertension, which may lead to severe headaches. Other symptoms of catecholamine release include palpitations, sweating, nausea, anxiety, and tingling in the extremities.
Pheochromocytomas are rare and about 90% of them are located in the adrenal glands. While a few pheochromocytomas are cancerous, most are benign and do not spread beyond their original location. Left untreated, however, they may continue to grow and symptoms may worsen. Over time the hypertension caused by the excess catecholamines may lead to kidney damage, heart disease, and raise the risk for stroke or heart attack.
Urine and blood catecholamine testing can be used to help detect the presence of pheochromocytomas. 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.
The blood catecholamines test measures the amount of hormones present in the blood at the moment of collection, while the urine test measures the amounts excreted over a 24-hour period.
How is the sample collected for testing?
For the 24-hour urine collection, all urine should be saved for a 24-hour period. It is important that the sample be refrigerated during this time period.
Blood for catecholamine testing is collected by inserting a needle into a vein in the arm. Although there is some disagreement over the specifics of how the sample should be collected, it may be necessary to lie down and rest quietly for 15 to 30 minutes prior to and during blood collection. In other circumstances, a person 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 blood and urine catecholamines are affected by certain drugs, foods, and stresses. Inform the doctor of all medications being taken and follow any instructions given to ensure that an appropriate sample is collected. For blood testing, fasting may be required.