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Introduction To Body Metanephrines
Metanephrine is used to describe the chemical byproduct of the catecholamine hormone epinephrine after it is broken down. Epinephrine is also known as “adrenaline" and it is produced in cases of “flight or fight." The main organ that produces epinephrine is the adrenal gland.
In stressful situations, epinephrine is used to caused the muscles to tense and get them ready for action. More muscle glycogen is broken down to mobilize glucose, and stored fat is rapidly converted to glucose, also.
When epinephrine encounters the heart muscle, it causes an increase in the heartbeat with more oxygen and glucose being sent to this muscle. In response to an increase heartbeat in the presence of epinephrine, the body also increases its breathing rate. In other areas of the circulatory system, blood is diverted away from organs such as the skin and digestive system in preparation for flight or a fight. Therefore, in the presence of epinephrine, the body undergoes quite a physiological change.
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How Epinephrine Is Released & Metanephrine Is Formed
However in certain tumors of the adrenal gland, the tumor cells will produce too much epinephrine and the body seems to be always in this constant state of “flight or fight." The most common adrenal tumor that produces elevated urine metanephrines is called a pheochromocytoma.
If the physician suspects that the person might have this disease they will order plasma or urine metanephrines testing to rule out any other possible reasons for the patient having similar signs and symptoms. If the reason for the patient’s symptoms is due to a pheochromocytoma, then this tumor can be removed before the illness becomes more severe.
Since a person’s metanephrine level can fluctuate over time, a full twenty-four hour sample of urine is collected. In some instances, a urine test is preferred over a blood test for metanephrine as they might show in the urine for a longer time than in the blood, as the body’s natural response is to filter the blood quickly and keep it clean.
This test is also able to help in the diagnosis of hard to control high blood pressure if there are other common symptoms associated with it. In some cases, the person with a tumor in the adrenal gland can have urine metanephrines tests ordered if they show no symptoms. This can help the physician with the diagnosis of the tumor’s location. In a few instances, a physician can order this laboratory test if there is a strong family history of pheochromocytoma
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What Does An Elevated Level Mean?
If there are elevated urine metanephrines, then it is up to the physician to discover the exact cause for the increased amount of urine metanephrines. Recall that epinephrine is produced in stressful situations, but can also be increased with certain medications or infections.
Even though metanephrines are produced in high quantities by a pheochromocytoma, a positive urine test will not always indicate that a tumor is present. Therefore, the physician will need to complete further tests, for example, ultrasound scan or even a biopsy, before the correct diagnosis can be made.
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Web Source: American Association for Clinical Chemistry. "Urine Metanephrines". 2010. Available at: http://www.labtestsonline.org/understanding/analytes/urine_metanephrine/test.html