Gamma-glutamyl transferase (GGT), earlier referred to as GGTP (gamma-glutamyl transpeptidase), is an enzyme found in large amounts in the liver, kidney and pancreas. When elevated in the blood it is most often a sign of liver disease. The GGT is not routinely tested because it is very sensitive to even minor changes in the liver. Medications are the most common cause of GGT elevation. The only use of the GGT is to determine whether alkaline phosphatase elevation (one of the liver tests) comes from the liver. Alkaline phosphatase elevation can be because of bone disease, but in that case the GGT is not elevated.