| GGT and 5'-NT
Gammaglutamyltransferase (GGT)
Located primarily in hepatocytes and to a lesser extent in a number of
other organs
Highly sensitive to hepatocyte damage and cholestasis
Elevated in chronic alcohol consumption and binge drinking
Also elevated by extensive reparative processes, drugs (phenytoin and
phenobarbital), obesity
Not elevated by bone disease, pregnancy, or childhood and adolescence
Used as a confirmatory test to indicate a hepatic origin for ALP elevation
(GGT can be elevated in co-existing conditions, so interpret its results
carefully and with consideration of the whole clinical picture)
5' -Nucleotidase
Provides confirmation for a hepatic origin for elevated ALP similar to
GGT
More specific for the liver and for cholestasis than GGT (which is generally
elevated with any type of hepatocellular injury)
Controversial as to whether GGT or 5'-NT provides the best confirmatory
test; in the past, 5'-NT has been more difficult to perform and thus less
generally available
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