Gamma-Glutamyl Transferase (GGT)

Overview

Gamma-glutamyl transferase (GGT) measures an enzyme predominantly located on the canalicular membrane of hepatocytes and biliary epithelial cells that catalyzes the transfer of gamma-glutamyl groups from glutathione to acceptors. It plays a role in amino acid transport and detoxification of xenobiotics. Elevated levels primarily indicate hepatobiliary disease (cholestasis, alcohol-related liver injury) or enzyme induction by drugs/alcohol, while low levels lack clinical significance. GGT is clinically useful for detecting liver disease, confirming alcohol abuse, and monitoring alcohol abstinence due to its sensitivity to ethanol induction.

Clinical Use Cases

  • Detecting chronic alcohol consumption and monitoring sobriety.
  • Evaluating cholestatic liver disease patterns.
  • Investigating elevated alkaline phosphatase origin (hepatic vs bone).
  • Assessing drug-induced liver injury (enzyme induction).

Specimen Types

  • Serum.
  • Plasma (lithium heparin).

Measurement Methods

  • IFCC kinetic spectrophotometric method (Szasz modification).
  • Automated clinical chemistry analyzers.

Test Preparation and Influencing Factors

  • No fasting required.
  • Alcohol, barbiturates, phenytoin, and rifampin induce elevated levels.
  • Obesity and diabetes associated with higher baseline GGT.
  • Children have lower reference ranges than adults.

Synonyms

  • Gamma-glutamyl transpeptidase.
  • GGTP.
  • GGT.

Further Reading

  • GGT Test; MedlinePlus;