Gamma-glutamyl transpeptidase

Alternative names:

gamma-GT; GGT; GGTP

What the risks are:

• excessive bleeding
• fainting or feeling lightheaded
• hematoma (blood accumulating under the skin)
• infection (a slight risk any time the skin is broken)
• multiple punctures to locate veins

Why is this test performed:
This test is used to detect diseases of the liver, bile ducts, and kidney; and to differentiate liver or bile duct (hepatobiliary) disorders from bone disease.

GGT participates in the transfer of amino acids across the cellular membrane and in glutathione metabolism. High concentrations are found in the liver, bile ducts, and the kidney.

GGT is measured in combination with other tests. In particular, ALP is increased in hepatobiliary disease and bone disease. GGT is elevated in hepatobiliary disease, but not in bone disease. So, a patient with an elevated ALP and a normal GGT probably has bone disease, not hepatobiliary disease.

Special considerations:

Drugs that can increase GGT levels include alcohol, phenytoin, and phenobarbital.

Drugs that can decrease GGT levels include clofibrate and oral contraceptives (birth control pills).

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.