Catecholamines - Urine

Pictures & Images

See all Pictures & Images

Why is the Test Performed?

The test is used primarily to screen for, diagnose, and monitor treatment of pheochromocytoma or neuroblastoma.

Catecholamines are chemically similar small molecules derived from the amino acid tyrosine. The major catecholamines are dopamine, norepinephrine, and epinephrine (old name: adrenalin).

Dopamine is a neurotransmitter (a chemical used to transmit impulses between nerve cells) found mainly in the brain. Norepinephrine is the primary neurotransmitter in the sympathetic nervous system (controls the "fight or flight" reaction) and is also found in the brain. Epinephrine is not only a brain neurotransmitter, but also a major hormone in the body.

Epinephrine is secreted from the adrenal medulla in response to low blood glucose, exercise, and various forms of acute stress (in the latter case, the brain stimulates release of the hormone). Epinephrine causes a breakdown of glycogen to glucose in liver and muscle, the release of fatty acids from adipose tissue, vasodilation of small arteries within muscle tissue, and increases the rate and strength of the heartbeat.

All of the catecholamines are metabolized by their target tissues or by the liver to become inactive substances that appear in the urine:

• dopamine becomes HVA
• norepinephrine becomes normetanephrine and VMA
• epinephrine becomes metanephrine and VMA