Gamma-glutamyltransferase is a transferase that catalyzes the transfer of gamma-glutamyl functional groups from molecules such as glutathione to an acceptor that may be any amino acid, a peptide or water. Gamma-glutamyl transferase (GGT) is also an enzyme found in many organs throughout the body, with the highest concentrations found in the liver. GGT is elevated in the blood in most diseases that cause damage to the liver or bile ducts. This test measures the level of GGT in a blood sample.
This test is often done with other tests that measure liver enzymes if there’s a possibility of liver damage. It is also done to evaluate for possible liver disease or bile duct disease or to differentiate between liver and bone disease as a cause of elevated alkaline phosphatase (ALP), sometimes to screen for or monitor alcohol abuse
The GGT test is sometimes used to help detect liver disease and bile duct obstructions. It is usually ordered in conjunction with or as follow up to other liver tests such as ALT, AST, ALP, and bilirubin. GGT can be used to screen for chronic alcohol abuse (it will be elevated in about 75% of chronic drinkers) and to monitor for alcohol use and/or abuse in people who are receiving treatment for alcoholism or alcoholic hepatitis.
Test results/ outcome:
The gamma-glutamyltransferase (GGT) test may be used to determine the cause of elevated alkaline phosphatase (ALP). Therefore, if the GGT level is normal in a person with a high ALP, the cause of the elevated ALP is the most likely bone disease. An elevated GGT level suggests that a condition or disease is damaging the liver but does not indicate specifically what. A low or normal GGT test result indicates that it is unlikely that a person has liver disease or has consumed any alcohol.