Synonyms: Gamma-glutamyl transpeptidase, GGT
Related tests: AST (GOT), ALT (GPT), Alkaline phosphatase, Bilirubin
Clinical significance
γGT (gamma-glutamyl transpeptidase, or GGT) is an enzyme that transfers the γ-glutamyl group from a γ-glutamyl peptide to another peptide or to an amino acid.
γGT is present in many tissues, but especially in the cells of the kidney tubules, the pancreas and the liver; in fact, it is mainly liver diseases with bile stasis that increase the synthesis of this enzyme, which is then released into the blood. Increases in serum γGT may be caused by kidney diseases (kidney tumours, nephrotic syndrome, diabetic nephropathy) and pancreatic diseases (pancreatic cancer, chronic pancreatitis).
γGT is an enzyme that can be induced (enzyme induction): certain substances (see below, warnings/interference), when taken long term, can increase the synthesis of this enzyme and therefore its release into the blood.
Hyperthyroidism and pregnancy can also cause an increase in γGT.
Clinical indications
Jaundice, surveillance of pancreatic and prostate cancers, suspected alcohol abuse.
Sample type
The patient must have a blood sample taken.
Preparation
You must fast for at least 8 hours; a small amount of water is allowed. You must have been standing or sitting upright for at least 30 minutes.
Notes
A true increase in serum γGT due to enzyme induction may be caused, in vivo, by long-term alcohol intake and long-term treatment with barbiturates, cephalosporins, oestrogens, oral contraceptives, phenytoin, primidone and propoxyphene.