Gammaglutamyl transferase is elevated in a number of hepatobiliary conditions (nearly all forms of biliary disease and cholestasis will be associated with a raised GGT (1)). These include:
- obstructive lesions of the biliary tree, whatever the site
- alcoholic liver disease: not specific for alcohol abuse but highly indicative if very raised relative to transaminases or alkaline phosphatase
- infectious disease: mild rise only
- of particular use in distinguishing hepatic disease at times of childhood growth spurts and during pregnancy as the specificity of alkaline phosphatase is reduced at this time (i.e. if a patient has an isolated raised alkaline phosphatase (high ALP with normal serum aminotransferases) an elevated GGT suggests the ALP is of liver origin)
The raised level of GGT must be interpreted in the context of other liver function tests. Mild liver disease tends to result in a ratio of alanine transaminase (ALT) to aspartate transaminase (AST) of greater than 1 and therefore with an AST of 30 and an ALT of 60, a patient with a non-alcoholic fatty liver would have a raised GGT.
More extensive liver disease tends to result in an ALT to AST ratio of less than 1 and therefore a raised GGT with an AST of 70 and an ALT of 30 is compatible (but not diagnostic of) alcohol damage.
In a patient who is known to abuse alcohol; if the AST and ALT are normal then the GGT may provide an indicator of recent alcohol intake.
Note though that there are many other non-hepatobiliary causes of a raised GGT and some of these are described in the linked GGT page below. Also reference values may vary between laboratories.
Pulse (2002), 62 (16), 84.