GGT1 and Decreased liver function: Even though serum GGT measurements are routinely used as a clinical laboratory test to detect liver dysfunction, bile duct conditions, and alcohol consumption-related damage4, it is unknown whether the elevated serum GGT derives from the same source in hepatobiliary diseases, nor is there direct evidence that serum GGT derives from the liver since increased hepatic GGT is apparently unnecessary to elevate the serum GGT level [71].