Gamma-glutamyltransferase (GGT) is a membrane-bound glycoprotein enzyme
catalyzes the transfer of the gamma-glutamyl moiety of glutathione to various peptide acceptors
chronic ethanol consumption is known to readily induce a rise in serum GGT
there is a positive correlation between ethanol intake and serum GGT activity
the WHO/ISBRA collaborative project on markers of alcoholism indicated elevated serum GGT concentrations in 52% of alcohol-dependent subjects (1)
the sensitivity of GGT as an alcohol marker has usually shown to be higher for men than for women (1)
due to the lack of specificity, GGT is a poor marker when alcohol consumption needs to be screened in patients with non-alcoholic liver diseases or in hospitalised patients
GGT is increased in all forms of liver disease, particularly in cases of intra- or posthepatic biliary obstruction
small increases (2-5 times normal) are observed in fatty liver
in alcoholics, serum GGT may help to distinguish those with or without liver disease
interpretation of GGT with respect to ALT and AST
raised level of GGT must be interpreted in the context of other liver function tests (2)
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
alcohol cessation and relation to GGT
increased activities usually return to normal if the patient abstains from alcohol with a normalization time of 2-3 weeks
helping to distinguish those with or without liver disease and relationship to normalization of GGT
persistently abnormal values in the absence of continuing ethanol exposure suggest liver disease, typically when GGT is initially 8-10 times normal and if the elevation persists after 6-8 weeks of abstention from alcohol (1)
if initial GGT levels are only 2-3 times normal and return to normal after abstention, the patient is likely to be devoid of liver disease (1)
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