Urine Metanephrines Test

This test is used to help diagnose or rule out a pheochromocytoma (tumor of the adrenal gland) or other neuroendocrine tumor.

This test measures the amount of metanephrines that are excreted in the urine over a 24-hour period. Metanephrines are breakdown products of the catecholamines, epinephrine (adrenaline) and norepinephrine. Catecholamines are a group of similar hormones produced in the nervous system and in the adrenal glands. The adrenal glands are small, triangular organs located on top of each kidney. The primary catecholamines are dopamine, epinephrine (adrenaline), and norepinephrine. These hormones 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 (small air passages in the lungs), 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 form 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.

Urine metanephrine testing measures the amount of both metanephrine and normetanephrine. These metabolites are usually present in the urine in small fluctuating amounts that increase appreciably during and shortly after the body is exposed to a stressor. Pheochromocytomas (rare adrenal gland tumors) 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. The catecholamines that pheochromocytomas produce can cause persistent hypertension (high blood pressure) and/or bouts or episodes of severe hypertension. This can cause symptoms such as headaches, palpitations, sweating, nausea, anxiety, and tingling in the extremities. About 90% of pheochromocytomas are located in the adrenal glands. While a few are cancerous, most are benign.

PREPARATION FOR TEST

For the 24-hour urine collection, all of your urine should be saved for a 24-hour period. It is important that the sample be refrigerated during this time period. Since diet, exercise, and drugs may affect metanepherine levels, precautions need to be taken to assure that the sample reflects a true metabolic condition and not an interference or aberration. For this reason you should talk to your caregiver about your diet and any medications you are taking. Foods such as coffee (including decaf), tea, chocolate, vanilla, bananas, oranges and other citrus fruits should be avoided for several days prior to the test and during collection. There are also many medications that can potentially affect test results. Talk to your caregiver about the prescriptions and over the counter drugs and supplements that you are taking. Wherever possible, those that are known to interfere should be discontinued prior to and during sample collection. Emotional and physical stresses and vigorous exercise should be minimized prior to and during test collection as they can increase catecholamine secretion.

NORMAL FINDINGS

  • Metanephrine

  • Less than 1.3 mg/24 hr or Less than 7 micromole/day (SI units)

  • Normetanephrine

  • 15-80 mcg/24 hr or 89-473 nmol/day (SI units)

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.