Norepinephrine is a neurotransmitter, or a chemical released by the nerves to stimulate cells. Sometimes, norepinephrine is recycled. Other times, it is broken down by enzymes and its products are excreted. Metanephrine is one of the products. Seeing how much metanephrine is in a 24-hour urine sample indicates how much the body has produced. There are three main diseases that cause high metanephrine levels in the urine.
Pheochromocytoma
Pheochromocytoma is a tumor that is usually found in the adrenal glands. It is in the inner part of the gland, or in the adrenal medulla. As explained by Ashley Grossman, M.D., Professor of Neuroendocrinology at the London School of Medicine in "The Merck Manual," the tumor secretes epinephrine, norepinephrine, dopa and dopamine. To remember the characteristics of this tumor, medical students remember the "rule of 10's." Ten percent of pheochromocytomas are malignant, 10 percent will calcify, 10 percent are found in children, 10 percent are extra-adrenal or found outside of the adrenal glands, 10 percent are bilateral or in both adrenal glands and 10 percent are familial. As such, most pheochromocytomas are not familial, which means they do not affect a lot of the members of the same family. The symptoms of pheochromocytoma include what medical students call "the 5 P's." The tumor causes the pain of a headache, palpitations, perspiration, pallor and pressure, meaning high blood pressure.
Neuroblastoma
Unlike the pheochromocytoma, the neuroblastoma is a tumor of children. Fifty percent of the cases of neuroblastoma are diagnosed before children are 2 years old. Physicians diagnose 90 percent of the cases before children reach the age of 5, according to Kelley Maloney, M.D., Associate Professor at the University of Colorado School of Medicine in "Current Diagnosis & Treatment: Pediatrics." The tumor can develop anywhere within the body. The symptoms that children have will depend upon the location of the tumor. They may have proptosis, or where a tumor behind the eyeball makes the eyeball stick out. They may have bruising around the eye, which has the nickname of "raccoon eyes," or there can be tumors right underneath the skin. Children can also have opsoclonus and myoclonus, or chaotic eye and muscle movements. The eye movements are due to tumors in the cerebellum of the brain. They may have symptoms of bone pain if the tumor spreads to the bone, or they can have pancytopenia, if it spreads to the bone marrow. Pancytopenia is a severe decrease of red blood cells, white blood cells and platelets, because the blood cells are made in the bone marrow and the tumor is interfering with their production. The children may also have weight loss, hypertension, fever and be very irritable. And there can be a mass in their abdomens.
Ganglioneuroma
Katie Nason, M.D., Assistant Professor at the University of Pittsburgh Medical Center writes in "Schwartz's Principles of Surgery," that ganglioneuromas are benign tumors. They are usually seen in young adults. People normally do not have any symptoms. However, as in the case of pheochromocytomas and neuroblastomas, ganglioneuromas will cause high metanephrine levels in the urine.
References
- "Current Diagnosis & Treatment: Pediatrics"; William Hay, Jr., M.D., Myron Levin, M.D., Judith Sondheimer, M.D., Robin Deterding, M.D.; 2009
- "Schwartz's Principles of Surgery"; F. Charles Brunicardi, M.D.; 2010
- The Merck Manual for Healthcare Professionals: Pheochromocytoma
