What is Copper?
Copper is an essential mineral that the body incorporates into enzymes. These enzymes play a role in the regulation of iron metabolism, formation of connective tissue, energy production within cells, the production of melanin (the pigment that produces skin color), and the function of the nervous system. This test measures the amount of copper in the blood, urine, or liver (hepatic).
Copper is found in many foods including nuts, chocolate, mushrooms, shellfish, whole grains, dried fruits, and liver. Drinking water may acquire copper as it flows through copper pipes, and food may acquire it when people cook or serve food in copper dishes.
- Normally, the body absorbs copper from food or liquids in the intestines, converts it to a non-toxic form by binding it to a protein, and transports it to the liver.
- The liver stores some of the copper and binds most of the rest to another protein called apoceruloplasmin to produce the enzyme ceruloplasmin. About 95% of the copper in the blood is bound to ceruloplasmin, and most of the rest is bound to other proteins such as albumin.
- Only a small amount is normally present in the blood in a free (unbound) state.
- The liver eliminates excess copper into the bile and it is removed from the body in the stool. Some copper is also eliminated in the urine.
Both excess and deficiency of copper are rare. Wilson disease, a rare inherited disorder, can lead to excess storage of copper in the eyes, liver, brain, and other organs. Copper excess (toxicity) can also occur by absorbing large amounts over a short period of time (acute exposure) or various amounts over a long period (chronic exposure).
Copper deficiency may occasionally occur in conditions associated with severe malabsorption, such as cystic fibrosis and celiac disease, and in infants exclusively fed cow-milk formulas. It can also occur in malnourished children as well as people who megadose zinc-containing vitamins.
A rare X-linked genetic condition called Menkes kinky hair syndrome leads to copper deficiency in the brain and liver of affected infants. The disease, which affects primarily males, is associated with seizures, delayed development, abnormal artery development in the brain, and unusual gray brittle kinky hair.
How is the test used?
Copper testing is primarily used to help diagnose Wilson disease, a rare inherited disorder that can lead to excess storage of copper in the liver, brain, and other organs. Less commonly, a copper test may be used to detect copper excess due to another condition, to detect a copper deficiency, or to monitor treatment for one of these conditions.
Typically, a total blood copper test is ordered along with a ceruloplasmin level. If the results from these tests are abnormal or unclear, then they may be followed by a 24-hour urine copper test to measure copper elimination and/or a copper test performed on a liver biopsy to evaluate copper storage in the liver.
Sometimes a free (unbound) blood copper test is also ordered. If Wilson disease is suspected, genetic testing may be performed to detect mutations in the ATP7B gene. However, these tests have limited availability and are usually performed in special reference or research laboratories.
Rarely, a copper test may be used to help diagnose Menkes kinky hair syndrome, a rare inherited disorder of copper transport dysfunction (see below).