Urine metanephrines

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Also known as: Metanephrine; normetanephrine
Formal name: Urine metanephrines, total and fractionated

At a Glance

Why Get Tested?

To help diagnose or rule out a phaeochromocytoma or other neuroendocrine tumour

When to Get Tested?

If you have symptoms of persistent or episodic high blood pressure such as severe headaches, rapid heart rate, and sweating

Sample Required?

Test Preparation Needed?

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 doctor about any 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 minimised prior to and during test collection as they can increase catecholamine secretion.

The Test Sample

What is being tested?

This test measures the amount of metanephrines that are excreted in the urine over a 24-hour period. Metanephrines are the inactive metabolites of the catecholamines adrenaline (epinephrine) and noradrenaline (norepinephrine). Catecholamines are a group of similar hormones produced in the nervous system and in the medulla (central portion) of the adrenal glands. The adrenal glands are small, triangular organs located on top of each kidney. 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. Noradrenaline also constricts blood vessels (increasing blood pressure) and adrenaline increases heart rate and metabolism. After completing their actions, the hormones are metabolised to form inactive compounds. Dopamine becomes homovanillic acid (HVA), noradrenaline breaks down into normetanephrine and 4-hydroxy-3-methoxymandelic acid (HMMA), sometimes known as vanillylmandelic acid (VMA), and adrenaline becomes metanephrine and HMMA. 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. Phaeochromocytomas and other neuroendocrine tumours, 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 phaeochromocytomas 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 phaeochromocytomas are located in the adrenal glands. While a few are cancerous, most are benign – they do not spread beyond their original location - although most do continue to grow. Left untreated, the symptoms may worsen as the tumour grows and, over a period of time, the hypertension that the phaeochromocytoma causes may damage body organs, such as the kidneys and heart, and raise the risk of an affected patient having a stroke or heart attack.

The metanephrine test can be used to help detect the presence of phaeochromocytomas. It is important to diagnose and treat these rare tumours because they cause a potentially curable form of hypertension. In most cases, the tumours can be surgically removed and/or treated to significantly reduce the amount of catecholamine being produced and to reduce or eliminate associated symptoms and complications.

How is the sample collected for testing?

For the 24-hour urine collection, all of your urine should be saved for a 24-hour period. It is important that the sample is collected into a bottle with preservative, and is refrigerated during this time period. The collection bottle will be supplied by your doctor or laboratory.

Is any test preparation needed to ensure the quality of the sample?

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 doctor about any 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 minimised prior to and during test collection as they can increase catecholamine secretion.

The Test

Common Questions

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