Nor Metanephrines, Urine Test
Nor Metanephrines, Urine Test
Nor metanephrines (normetanephrine) are metabolites of norepinephrine, a neurotransmitter involved in the body's fight-or-flight response. The Nor Metanephrines, Urine Test measures the levels of normetanephrine excreted in urine, helping diagnose pheochromocytomas and paragangliomas, rare tumors that produce excessive catecholamines, leading to high blood pressure and cardiovascular complications.
This test is often used alongside the plasma metanephrines test to confirm abnormal catecholamine production. It is a useful, non-invasive diagnostic tool for evaluating episodic hypertension and related symptoms.
What is the Nor Metanephrines, Urine Test Used For?
This test is used to:
- Detect pheochromocytomas and paragangliomas.
- Evaluate unexplained high blood pressure (hypertension).
- 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
Avoid caffeine, alcohol, and tobacco for 24 hours before and during urine collection.
Refrain from certain medications (e.g., antidepressants, decongestants, and blood pressure medications) as instructed by your doctor. Follow a low-tyramine diet, avoiding bananas, chocolate, vanilla, and fermented foods for 2 days before testing. 24-hour urine collection is required; all urine over 24 hours must be collected in a special container.
Interpretation of Results
- Elevated Nor Metanephrines (>2000 µg/day): Suggests the presence of a pheochromocytoma or paraganglioma, warranting further imaging (MRI or CT scan) to locate the tumor.
- Mild Elevation (600–2000 µg/day): May result from stress, diet, or medications.
- Normal Levels (<600 µg/day): Typically rule out catecholamine-secreting tumors.
FAQs
Is the urine test better than the plasma test for detecting pheochromocytomas?
Both tests are highly sensitive, but plasma metanephrines may detect tumors earlier, while urine testing provides a more complete picture of catecholamine secretion over time.
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