Nor Metanephrines, Free - Plasma Test
Nor Metanephrines, Free - Plasma Test
Nor metanephrines (normetanephrine) are metabolites of norepinephrine, a hormone and neurotransmitter involved in the body's fight-or-flight response. The Nor Metanephrines, Free - Plasma Test measures the level of free normetanephrine in the blood to help diagnose pheochromocytomas and paragangliomas, which are rare tumors that cause excessive catecholamine production.
These tumors can lead to severe hypertension, rapid heart rate, headaches, and excessive sweating. Early detection through plasma normetanephrine testing is essential, as untreated pheochromocytomas can result in life-threatening cardiovascular complications.
What is the Nor Metanephrines, Free - Plasma Test Used For?
This test is used to:
- Diagnose pheochromocytomas and paragangliomas.
- Evaluate unexplained high blood pressure that is resistant to treatment.
- Monitor recurrence of catecholamine-secreting tumors after treatment.
- Assess patients with genetic syndromes linked to adrenal tumors, such as Multiple Endocrine Neoplasia (MEN) type 2 and Von Hippel-Lindau (VHL) syndrome.
Symptoms of Pheochromocytomas and Paragangliomas
Excessive catecholamine production can cause
Persistent or episodic high blood pressure
Severe headaches
Excessive sweating (diaphoresis)
Rapid or irregular heartbeat (tachycardia/palpitations)
Anxiety, nervousness, or panic attacks
Unexplained weight loss
Preparation for the Test
Fasting for 8–10 hours before the test is recommended. Avoid caffeinated drinks, alcohol, and tobacco for at least 24 hours before testing. Refrain from consuming certain medications (e.g., antidepressants, decongestants, and blood pressure medications) if advised by a healthcare provider. Relax for 30 minutes before blood collection to avoid stress-induced elevations in normetanephrine levels.
Interpretation of Results
- Highly Elevated Nor Metanephrines (>4.0 nmol/L (>800 pg/mL))- Highly indicative of a catecholamine-secreting tumor
- Elevated Nor Metanephrines (>2.0 nmol/L (>400 pg/mL)): Suggest the presence of a pheochromocytoma or paraganglioma, requiring further imaging (MRI or CT scan) to locate the tumor.
- Mild Elevation (0.90–2.0 nmol/L (180–400 pg/mL)): May be due to stress, medication, or other underlying conditions.
- Normal Levels (Typically <0.90 nmol/L (or <180 pg/mL)): Typically rule out catecholamine-secreting tumors.
FAQs
How accurate is the plasma free normetanephrine test?
It is the most sensitive test for detecting pheochromocytomas, with over 95% accuracy.
Can medications affect the test results?
Yes, drugs like antidepressants, blood pressure medications, and decongestants can interfere with results. Consult your doctor about medication adjustments before testing.
What happens if my test result is abnormal?
Additional urine metanephrine tests, imaging (MRI or CT scans), and genetic testing may be needed to confirm a diagnosis.
Who should get this test?
People with unexplained high blood pressure, symptoms of excessive catecholamine release, or a family history of pheochromocytomas should consider this test.
Can pheochromocytomas be treated?
Yes, treatment includes surgical removal of the tumor, with medication management for blood pressure before surgery.
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