γ-glutamyltransferase

Background

• Liver enzyme in microsomes that catalyzes transfer of γ-glutamyl group from peptides to other amino acids

Interpretation

• About 90% sensitive for cholestasis (with ALP)
  • Often only rise after several days
• Isolated elevation of GGT may be caused by enzyme induction from alcohol or aromatic medications, without liver disease1
  • Aromatic medications include, commonly, phenobarbital, phenytoin, and others
  • Elevation is usually about twice the upper limit of normal
• Can also see isolated elevations in COPD, AKI or CKD, and acute myocardial infarction2
• May be elevated in NAFLD and hepatitis C and other liver or biliary diseases