Gamma-glutamyl transferase (GGT)

What it measures

GGT is a membrane enzyme abundant in the liver and bile ducts. It is a sensitive marker of cholestasis and of enzyme induction by alcohol and certain drugs, and helps confirm the liver origin of a raised ALP.

Specimen and preparation

• Specimen: Serum or lithium-heparin plasma
• Tube: Gold top

Reference range

Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.

Causes of high values

• Cholestasis or biliary obstruction
• Regular alcohol intake
• Enzyme-inducing drugs (phenytoin, carbamazepine)
• Fatty liver disease
• Hepatitis and liver tumours
• Pancreatitis

Method

Kinetic colorimetric assay (IFCC, glutamyl-carboxy-nitroanilide)

Good to know

GGT is not raised by bone disease, which makes it useful for interpreting an isolated high ALP.

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