• A liver/biliary enzyme that is especially useful in the diagnosis of obstructive jaundice, intrahepatic cholestasis, and pancreatitis. GGTP is more responsive to biliary obstruction than are aspartate aminotransferase (AST) (SGOT) and alanine aminotransferase (ALT) (SGPT).
• Increased in hepatoma and carcinoma of pancreas. Useful in diagnosis of metastatic carcinoma in the liver. Increasing levels in carcinoma patients relate to tumor progression, and diminishing levels to response to treatment. CEA, alkaline phosphatase, and GGTP used together are useful markers for hepatic metastasis from breast and colon primaries. GGTP is elevated in some instances of seminoma.
• Useful in diagnosis of chronic alcoholic liver disease, but some heavy drinkers do not have GGTP increases. Serial determinations of serum GGTP, AST, and ALT levels can distinguish recovering alcoholics who resume drinking from those who remain abstinent. Increase in body mass is positively correlated with increased GGTP levels. With MCV of red cells, GGTP is useful as a test for alcoholism.
• GGTP is the test for cholestasis during or immediately following pregnancy. Commonly elevated in cirrhosis and hepatitis. The transaminases, AST and ALT rise higher in acute viral hepatitis; these tests with GGTP and other parameters are best used together in work-up of liver disease.
• Increased in systemic lupus erythematosus. Very high levels are common in primary biliary cirrhosis. High GGTP is found in infants with biliary atresia. It is increased with hyperthyroidism and decreased in those with hypothyroidism. GGTP is comparable in many ways to two other biliary tests, LAP and 5' nucleotidase. In some cases, five tests (including alkaline phosphatase and bilirubin) are necessary to evaluate the biliary tract. GGTP usually is the most sensitive.
• In ascitic fluid, very high GGTP is said to suggest hepatoma as opposed to cirrhosis or liver metastases.
• GGTP is helpful to work up elevated alkaline phosphatase values. GGTP is a biliary excretory enzyme which is more specific for hepatic disease than is alkaline phosphatase. It is normal in most instances of renal failure. GGTP has no origin in bone or placenta, unlike alkaline phosphatase, and age beyond infancy does not influence GGTP levels. Activity of GGTP is highest in obstructive liver disease. It is commonly elevated in patients with infectious mononucleosis. When GGTP and alkaline phosphatase are both high, but one is disproportionately elevated, suspect the possibility of drug-induced cholestasis (including alcoholism if it is GGTP which is much higher). GGTP, postprandial glucose, and triglyceride bear some correlation in certain groups of patients, including alcoholism and diabetes mellitus. Treatment of hypertriglyceridemia may also lead to decreased GGTP. GGTP is normal in normal children, adolescents, and in pregnant women. Unlike AST, it is not elevated in skeletal muscle disease.
• GGTP may be elevated also in some diseases of the kidneys and heart; yet, it is the most sensitive test for liver cell damage.
• Normal Ranges are 3.0 - 28.7 IU/L in Females, and 3.3 - 35.0 in Males.

Values obtained with different assay methods should not be used interchangeably.