Pheochromocytoma is a tumor that forms on the adrenal gland. Blood tests for pheochromocytoma measure plasma free metanephrine in the blood. The test is usually ordered when symptoms of pheochromocytoma, such as headaches, sweating, flushing, and rapid heart rate, are reoccurring.
What is Pheochromocytoma?
Pheochromocytoma is a tumor that develops in the adrenal gland. It is usually located within the adrenal medulla, which is the portion of the adrenal gland that produces adrenaline. The tumor causes the adrenal gland to produce too much adrenaline, which leads to an increase in blood pressure.
Some of the symptoms associated with pheochromocytoma include excess sweating, headaches, rapid heart rate, and nervousness. The tumor can develop at any time during a person's life. Individuals that are under 35 or over 60 and suddenly develop high blood pressure should get tested for pheochromocytoma.
Plasma Free Metanephrine Blood Test
The plasma free metanephrine blood test is one of the blood tests for pheochromocytoma. The test is usually ordered when an individual has symptoms that are characteristic of pheochromocytoma or has a family history of pheochromocytoma. It tests the blood for metanephrine and normetanephrine, which are metabolized forms of epinephrine and norepinephrine.
Metanephrine is found in the blood and urine. The blood test is considered much more sensitive than the urine test. So much so that it can lead to false positives. Since the blood test is very sensitive, it isn't used as a routine test.
Catecholamines Blood Test
Blood tests for pheochromocytoma that measure epinephrine, norepinephrine, or dopamine are called Catecholamine blood tests. Catecholamines are the hormones that are produced in the adrenal medulla of the adrenal gland. These hormones are released into the blood stream in response to stress. Norepinephrine constricts blood vessels, and epinephrine increases the heart rate and metabolism.
A catecholamine blood test is ordered when an individual is experiencing reoccurring symptoms that include headaches, excessive sweating, and high blood pressure. The test is also used to measure hormone levels after a pheochromocytoma has been removed to monitor for any new tumor growths.
How are the Blood Tests Performed
Both the plasma free metanephrine and the catecholamines blood test require a blood sample that is drawn from a vein in the arm. Inform your doctor of any medications that you are taking before giving your blood for testing. For the plasma free metanephrine test, the doctor may ask you to discontinue the use of drugs that contain epinephrine or acetaminophen before taking the test. Fasting is also required for the plasma free metanephrine test.
Blood Test Results
If the level of metanephrine or catecholamines in the blood is normal, then pheochromocytoma can be ruled out. If the plasma free metanephrine test shows elevated levels of metanephrine, the doctor may evaluate potential causes including medications, diet, and stress level. A second test is usually given to confirm the elevated results and an image scan is taken before pheochromocytoma is diagnosed. A similar approach is taken for elevated levels of catecholamine.
1. "Plasma Free Metanephrine." Lab Tests Online. American Association for Clinical Chemistry. 24 Nov. 2010. Web 10 Dec. 2010.
2. Norman, James. "Pheochromocytoma: A Tumor of the Central Adrenal." EndocrineWeb. Vertical Health LLC. 12 Oct. 2010. Web 10 Dec. 2010.
3. "Catecholamines, Plasma and Urine." Lab Tests Online. American Association for Clinical Chemistry. 24 Nov. 2010. Web 10 Dec. 2010.