Normetanephrine is a metabolite of norepinephrine. Normally, the levels of Normetanephrine are low in the plasma. However, when there are tumors in the body that originate from neural crest cells called paragangliomas or neuroblastomas, or from pheochromocytomas (an adrenal gland tumor), the levels of Normetanephrine rise significantly. When Normetanephrine levels are normal, then it’s extremely unlikely that someone has pheochromocytoma or paraganglioma.
If this test is positive, another type of test should be done, called the fractionated 24-hour urinary metanephrines.
One reason why low Normetanephrine levels may occur is because of ongoing Metyrosine treatment (This is the treatment for pheochromocytoma.)
Normetanephrine (NMN) is above the optimal range. NMN is the chief metabolite of norepinephrine. Research shows that urinary NMN levels are elevated in patients with ADHD (self-reported), suggesting overall higher tonic activity of the norepinephrine system (Pliszka, et. al. 1994). Additional symptoms of NMN excess usually include anxiety, headaches, high blood pressure and heart palpitations, implicating that norepinephrine metabolism runs in parallel in the brain and the rest of the body.
High levels of Normetanephrine can be from a pheochromocytoma. This is usually a benign tumor that stems from aberrant cells in the adrenal gland. The tumor produces hormones that cause high blood pressure. The high blood pressure can cause life-threatening situations, such as a heart attack.
Some specific causes of high levels of Normetanephrine may include:
- Monoamine oxidase inhibitors from tyramine-rich foods (bananas, chocolate, dried/smoked meats, cheese, beer/wine, aged or pickled foods, or nuts)
- Catecholamine reuptake inhibitor consumption (cocaine and local anesthetics, including lidocaine)
- Anesthetic gasses, especially one called halothane
- Going through the sedative drug withdrawal process from alcohol, valium, opioids, and the high blood pressure drug called Clonidine
However, the elevated levels caused by the above-mentioned items are not that significant.
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