Gamma-GT (gamma-glutamyl transferase)

Gamma-GT (gamma-glutamyl transferase, also GGT or γGT) is an enzyme located in the cell membrane of many organs – especially in the cells of the bile ducts and the liver, and also in the kidneys, pancreas and gut. The gamma-GT in the blood comes mainly from the liver and bile ducts. It is measured in serum together with GOT, GPT, alkaline phosphatase and bilirubin; the blood sample is taken in a practice.

What gamma-GT does in the body

Gamma-GT splits the glutamyl group off glutathione, the body's most important own antioxidant, and transfers it to amino acids or peptides. In this way glutathione outside the cells is broken down into its building blocks, so that the cells can take up again above all the scarce amino acid cysteine and use it to build new glutathione. Gamma-GT is thus part of the glutathione cycle, which shields cells against oxidative stress and is involved in detoxifying foreign substances in the liver. Production of the enzyme can be stimulated by alcohol and certain medicines.

Low gamma-GT – what happens in the body?

A low gamma-GT value is unremarkable and has no known disease meaning on its own. It indicates that there is neither bile congestion nor increased enzyme production in the liver. A special case are some rare inherited disorders of bile flow in which gamma-GT stays low despite bile congestion, because the defect affects the excretion of bile acids and does not damage the bile duct cells. Together with a raised alkaline phosphatase, a normal gamma-GT also shows that the rise is more likely to come from bone than from the liver.

Raised gamma-GT – what happens in the body?

A raised gamma-GT value arises in two ways: either the liver cells produce more enzyme – for example through regular alcohol consumption or certain medicines such as some anti-seizure drugs – or bile becomes congested and washes the enzyme out of the bile duct cells into the blood, for example with gallstones or inflammation of the bile ducts. Fatty liver also often raises gamma-GT. Studies have also linked a higher gamma-GT value with oxidative stress, overweight and insulin resistance; whether it is a cause or an accompanying feature has not been clarified.

The interpretation is given in your report.