Diagnostic Use
Assessment of Liver Disease
Gamma-Glutamyl transferase (GGT) is a glycoprotein enzyme located at the outer surface of cell membranes, responsible for catalysing the transfer of glutamyl groups from peptides to acceptors. It plays an important role in the extracellular metabolism of glutathione, a major thiol anti-oxidant.
Although high GGT can be found in many organs including kidneys, pancreas, prostate, the major contributor to circulating GGT activity is by the liver.
Traditionally GGT is included in the liver enzyme panel as a sensitive marker for liver conditions, especially in reflecting biliary tract (intra or extra-hepatic) damage associated with different cholestatic conditions. Of note is that, in Intrahepatic Cholestasis of Pregnancy and Progressive Familial Intrahepatic Cholestasis type 1 (PFIC 1), GGT can be normal or only mildly raised.
GGT can be a useful marker to help establish hepatic origin of rise in total alkaline phosphatase (ALP) as unlike ALP, GGT is not raised in bone related conditions nor during pregnancy.
GGT has been used as a crude index of heavy alcohol consumption independent of presence of alcoholic liver disease or not. Some medications e.g. phenytoin, phenobarbital, frusemide can also induce GGT.
There is an emerging role of GGT as an oxidative stress biomarker of cardiometabolic risk and cardiovascular disease.
Test Method
Principle: Enzymatic colorimetric
Analyser: Roche Diagnostics Cobas c703/c503
Reagent: GGT-2