Times change and my website needed to change too. To see the 2020 update of this page click this link
To see what normal blood and urine values are for your pet, go here
For an explanation of causes of most abnormal blood and urine tests go here
To see how tests are often grouped, go here
or GGT is an enzyme with far too many names.
No one is absolutely sure what its function is, (probably involved in metabolizing the amino acid, glutamine or glutathione peptides), but much of it is found in the cells that make up your pet’s liver (hepatocytes).
The level of many enzymes can rise when your pet’s liver is injured; but for most of them (such as AP and AST), other health problems can also cause elevated levels. High GGT levels, however, are close to 90% accurate in identifying the location of a problem (hepatobiliary disease, cholestasis) when it is indeed the liver that is the source of your pet's health problem.
Various types of liver damage will raise GGT levels in your pet’s blood. The test seems particularly sensitive for detecting liver damage in cats (in cats, GGT often rises sooner than AP), but is not that elevated in cats with hepatic lipidosis. GGT levels tend to rise significantly any time bile flow within your pet's liver is blocked (cholestasis). Bile duct obstructions (by gall stones or duct inflammation), liver tumors or secondary to pancreatic inflammation in cats can all cause high GGT levels.
medications can also raise GGT levels, as can drugs given to control epilepsy
(phenobarbital), biliary tract hyperplasia
or biliary tract inflammation (cholangiohepatitis).
The degree of elevation in GGT levels in your pet does not necessarily indicate how severe the liver problem in your pet is or will become.
In humans, low GGT has been associated with hypothyroidism or low blood magnesium levels. We do not know if that is true in pets as well.