To help diagnose or rule out a rare tumor of the adrenal gland called a pheochromocytoma or a rare tumor occurring outside the adrenal glands called a paraganglioma; these tumors (PPGL) produce excess hormones called catecholamines, which are broken down to metanephrines.
When your healthcare provider either suspects that you have a tumor that produces catecholamines or wants to rule out the possibility; when you (especially if you are younger than age 40) have sudden bursts (paroxysms) of signs and symptoms, such as high blood pressure (especially if it doesn’t respond to standard treatment), severe headaches, rapid heart rate (palpitations), sweating, tremors and flushing; when you have a hereditary (genetic) risk for developing PPGL; when a tumor has been treated or removed, to monitor for recurrence; occasionally, when an adrenal tumor is detected by chance, such as during an imaging test for another condition
A blood sample drawn from a vein
Blood for plasma metanephrine testing is collected by inserting a needle into a vein in your arm. Although you may be seated for the collection, it is recommended that you be lying down. The health care practitioner or the collection site will instruct you as to their specific requirements.
These tests are affected by certain drugs, foods, and stresses. Inform your healthcare practitioner of any medications you are taking and follow any preparation instructions you are given before sample collection.
The metanephrines – metanephrine and normetanephrine – are breakdown products (metabolites) of the catecholamines epinephrine (adrenaline) and norepinephrine. The plasma free metanephrines test measures the amount of metanephrine and normetanephrine in the blood.
Catecholamines are produced by the adrenal glands (as hormones), small triangular organs located on top of each kidney, and by cells of the sympathetic nervous system (called neurotransmitter substances or neurotransmitters). The primary catecholamines are dopamine, epinephrine (adrenaline), and norepinephrine. Catecholamines are released in response to physical or emotional stress. They help transmit nerve impulses in the brain, increase glucose and fatty acid release for energy, dilate small air passages in the lungs called bronchioles, and dilate the pupils. Norepinephrine also constricts blood vessels, which increases blood pressure, and epinephrine increases heart rate and the rate at which the body uses energy (metabolism).
After completing their actions, catecholamines are metabolized to inactive compounds. Epinephrine breaks down into metanephrine and vanillylmandelic acid (VMA) and norepinephrine becomes normetanephrine and VMA. Both the hormones and their metabolites are eliminated from the body in the urine.
Catecholamines and their breakdown products are normally found in small fluctuating quantities in the blood and urine and only increase appreciably during and shortly after a stressful situation.
However, rare tumors of the adrenal glands called pheochromocytomas and rare tumors that occur outside the adrenal glands called paragangliomas can produce large amounts of the hormones, resulting in significantly increased concentrations in both the blood and urine. (These syndromes are often grouped together and abbreviated as PPGL.) This can cause persistent or episodic periods of high blood pressure, which may lead to severe headaches. Other symptoms include 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 the symptoms may worsen. Over time, hypertension caused by the excess hormones may cause kidney damage, heart disease, and raise the risk of a stroke or heart attack.
Although they are rare, it is important to diagnose these tumors because they cause a potentially curable form of hypertension. In most cases, the tumors can be surgically removed and/or treated to eliminate or significantly reduce the amount of catecholamine being produced and to eliminate their associated symptoms and complications.
How is the sample collected for testing?
Blood for plasma free metanephrines testing is collected by inserting a needle into a vein in the arm. Although you may be seated for the collection, it is recommended that you be lying down. Your healthcare practitioner or the collection site will instruct you as to their specific requirements.
Is any test preparation needed to ensure the quality of the sample?
Catecholamine levels and by extension the levels of their metabolites are affected by various 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 your health care practitioner or the collection site or laboratory.
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