Plasma Free Metadrenalines (Metanephrines)
When you have persistent or episodic high blood pressure and symptoms such as headaches, rapid heart rate, and sweating
A blood sample is obtained by inserting a needle into a vein in the arm.
Not required. Please inform your healthcare professional of any medication (prescription and non prescription) that you are taking.
The plasma free metadrenalines test measures the amount of metadrenaline and normetadrenaline in the blood. These substances are metabolites of adrenaline (epinephrine) and noradrenaline (norepinephrine). Adrenaline and noradrenaline are catecholamine hormones that help regulate blood pressure.
Catecholamines are produced in the adrenal medulla – the interior portion of the adrenal glands – and secreted into the blood. Once these hormones have completed their actions, they are metabolised to inactive compounds. Noradrenaline breaks down into normetadrenaline and hydroxymethylmandelic acid (HMMA) (also called vanillylmandelic acid (VMA)), and adrenaline becomes metadrenaline and HMMA. Both of the catecholamines and their metabolites are normally found in small fluctuating quantities in the blood and urine.
A rare tumour called a phaeochromocytoma can produce large amounts of catecholamines, resulting in significantly increased concentrations of metadrenaline and normetadrenaline. About 80-85% of phaeochromocytomas form in the adrenal glands and, while a few are cancerous, most are benign – they continue to grow but usually do not spread beyond their original location.
The catecholamines produced by phaeochromocytomas can cause persistent hypertension and episodes of severe high blood pressure. This can cause symptoms such as headaches, palpitations, sweating, nausea, anxiety, and tingling in the extremities. Left untreated, the symptoms may worsen as the pheochromocytoma grows. Over time, hypertension caused by the tumour may cause kidney damage, heart disease, and raise the risk of a stroke or heart attack.
Several tests, including plasma free metadrenalines, can detect the presence of phaeochromocytomas. Although they are rare, it is important to diagnose these tumours because they cause a potentially curable form of hypertension. In most cases, the pheochromocytomas can be surgically removed, which eliminates the high blood pressure and its associated symptoms and complications.
How is it used?
Plasma free metadrenaline is a test used to help diagnose or rule out the presence of a phaeochromocytoma. Its primary use is in symptomatic people when urine testing does not provide clear-cut results.
Occasionally, the test may be requested on an asymptomatic person if an adrenal tumour is detected during a scan conducted for another purpose or if the person has a strong personal or family history of phaeochromocytomas. These tumours may recur, and there is a genetic link in some cases.
When is it requested?
What does the test result mean?
Since the plasma free metadrenalines test is very sensitive and phaeochromocytomas are rare, a doctor may see more false positives with this test than true positives. The negative predictive value of the test, however, is very good. This means that if the concentrations of metadrenaline and normetadrenaline are normal in the blood, then it is unlikely that a person has a phaeochromocytoma.
If levels are elevated in someone who has had a previous phaeochromocytoma, it may be an indication that the tumour is recurring.
Is there anything else I should know?
The majority of phaeochromocytomas are found in the adrenal glands and most of the rest are found within the abdominal cavity. While the plasma free metadrenalines test can help detect and diagnose phaeochromocytomas, it cannot tell the doctor where the tumour is or whether it is benign or malignant (although most are benign).
An increased risk for developing phaeochromocytomas can be inherited. Multiple endocrine neoplasia, type 2 (MEN-2) is a condition associated with alterations in specific genes. They increase the lifetime risk that those affected will develop tumours in one or more of their endocrine glands.
I have more than one pheochromocytoma at once?
Does the amount of plasma free metadrenalines detected correspond to the size of the tumour?