Normetanephrine

Normetanephrine

Pathway of noradrenaline breakdown, showing the formation of normetanephrine.

Normetanephrine is a metabolite of the catecholamine norepinephrine (also known as noradrenaline). It is produced by the action of the enzyme catechol-O-methyltransferase (COMT) on norepinephrine. Normetanephrine is an important compound in the diagnosis of certain medical conditions, particularly those related to the adrenal glands.

Biochemistry

Normetanephrine is formed when norepinephrine undergoes methylation by the enzyme catechol-O-methyltransferase. This reaction occurs primarily in the liver and kidneys. The chemical structure of normetanephrine is similar to that of norepinephrine, but with a methyl group added to the catechol hydroxyl group.

Metabolic Pathway

The breakdown of norepinephrine involves several steps:

1. Norepinephrine is released from sympathetic nerve endings and the adrenal medulla. 2. It is either taken back up into nerve terminals or metabolized. 3. When metabolized, norepinephrine is converted to normetanephrine by COMT. 4. Normetanephrine can be further metabolized to vanillylmandelic acid (VMA), which is excreted in the urine.

Clinical Significance

Normetanephrine levels in the body can be measured to assess the function of the adrenal glands and the sympathetic nervous system. Elevated levels of normetanephrine can indicate the presence of pheochromocytoma, a type of tumor that arises from the adrenal medulla and secretes excessive amounts of catecholamines.

Diagnostic Use

The measurement of normetanephrine in the plasma or urine is a useful diagnostic tool for detecting pheochromocytomas and other neuroendocrine tumors. It is often measured alongside metanephrine, another metabolite of catecholamines.

Related Pages

• Norepinephrine
• Catecholamine
• Pheochromocytoma
• Catechol-O-methyltransferase
• Vanillylmandelic acid