Test Name: Gamma-Glutamyl Transferase, Serum
GGT enzyme is a biliary excretory enzyme that is elevated specifically in response to hepatobiliary obstructive disease and is sensitive to
It is alcohol consumption
Application:
Help to diagnose obstructive jaundice, intrahepatic cholestasis and pancreatitis. Its main use is in the differential diagnosis of patients with increased alkaline phosphatase.
In biliary obstruction, GGT gives more response than SGOT and SGPT.
In obstructive disease, concentrations of 5 to 50 times normal are seen. In infectious hepatitis, the values are rarely more than 5 times normal. GGT increases in hepatoma and pancreatic carcinoma and helps in the diagnosis of metastatic carcinoma to the liver.
In breast and colon cancer patients, the use of ALP, CEA and GGT together is useful for investigating liver metastasis. GGT also increases in some cases of seminoma.
In chronic alcoholic liver disease, GGT is more than 2 times the upper level of the reference range and the ratio of AST to ALT is more than 2 strongly in favor of alcohol abuse.
Evaluation of cholestasis during pregnancy or immediately after pregnancy. It is commonly increased in cirrhosis and hepatitis. GGT also increases in SLE.
Very high concentrations are common in primary biliary cirrhosis.
It is also high in biliary atresia of babies. GGT increases in hyperthyroidism and decreases in hypothyroidism.
In the ascites fluid of some patients with hepatoma, in comparison with ascites caused by cirrhosis or metastasis, the ascites fluid of alcoholic cirrhosis is high.
Limitations:
The combination of high alkaline phosphatase and normal GGT does not completely rule out liver disease. GGT may decrease in late pregnancy. It has not been successful to be used only as screening for colorectal carcinoma metastasis to the liver before surgery.
Drug interactions:
Drugs that may cause a decrease in GGT include: azathioprine, conjugated estrogens, and methotrexate, while drugs that may cause an increase include acetaminophen, aminoglutamide, phenytoin, phenobarbital, carbamazepine, diphenylhydantoin, esterified estrogens, and interferon. Alpha-n3, medroxyprogesterone, OCP, phenothiazines, streptokinase, sodium valproate and alcohol.
Additional information:
GGT is more specific for liver disease than ALP. GGT is normal in most cases of kidney failure. Unlike ALP, GGT does not have a bone or placental origin, and after childhood, age has no effect on it. GGT is commonly elevated in patients with infectious mononucleosis.
When both GGT and ALP are high, but the increase of one of them is disproportionate to the other, the possibility of drug-induced cholestasis should be considered. In healthy children and adults and pregnant women, GGT will be normal and, unlike SGOT, it will not increase in skeletal muscle disease. The half-life of GGT is ten days, but in the recovery phase from alcohol abuse, it may be up to 28 days. GGT increases in 60 to 70% of those who have chronic alcohol abuse, and with abstinence from alcohol, the level of the enzyme often decreases slowly, but remains high for at least one month after abstinence.
With the use of phenytoin and carbamazepine, GGT increases up to five times the reference values.
Reference range:
It is higher in babies and the first 3 to 6 months of life. The values in males are 25% higher than females. In the elderly, it is slightly higher than in adults, and in infants it is five times higher than in adults.
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