Plasma metanephrines measurement is used for the diagnosis and laboratory documentation of catecholamine-secreting tumors such as pheochromocytomas and paragangliomas.
More Information
Metanephrine measurement is used to evaluate adrenal function. Metanephrines are usually determined when a patient with hypertension is suspected of having pheochromocytoma, which is a tumor of the adrenal medulla. Less than 1% of hypertensive patients have pheochromocytomas. Metanephrines (normetanephrine and metanephrine) are the main substances formed in the adrenal medulla, released into the bloodstream, and excreted in the urine. These substances contain a catechol nucleus and an amine group and belong to the catecholamines. Metanephrine and normetanephrine are metabolites of epinephrine and norepinephrine, respectively. Metanephrine and normetanephrine are then metabolized to vanillylmandelic acid (VMA). 3-Methoxytyramine (3MT) is the metabolite of dopamine. It is formed by introducing a methyl group to dopamine by the enzyme catechol-O-methyl transferase (COMT). 3-MT can be further metabolized by the enzyme monoamine oxidase (MAO) to form homovanillic acid (HVA), which is then typically excreted in the urine.
The traditional testing method is a 24-hour urine test (89-100% sensitivity) because blood testing has many interfering factors. Determination of metanephrines is the best test for diagnosing pheochromocytoma because metanephrine levels are not influenced by many factors that affect catecholamine levels (e.g., postural changes, exercise, surgical stress). At the same time, they have a better correlation with tumor size and fewer drug interventions than catecholamines.
Possible Interpretations of Pathological Values
- Increase: Adrenal tumors, brain tumors, ganglioneuroblastoma, ganglioneuroma, neuroblastoma, pheochromocytoma hypertension, malignant pheochromocytoma, pheochromocytoma, extensive metastases, myasthenia gravis, progressive muscular dystrophy, sepsis, severe stress
Important Note
Laboratory test results are the most critical parameter for diagnosing and monitoring all pathological conditions. 70% and 80% of diagnostic decisions are based on laboratory tests. Correctly interpreting laboratory results allows a doctor to distinguish "healthy" from "diseased."
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be analyzed based on each case and family history, clinical findings, and the results of other laboratory tests and information. Your physician should explain the importance of your test results.
At Diagnostiki Athinon, we answer any questions you may have about the test you perform in our laboratory and contact your doctor to ensure you receive the best possible medical care.
