From the Guidelines
GGT (Gamma-Glutamyl Transferase) is primarily used as a diagnostic blood test to evaluate liver function and detect liver disease or bile duct obstruction, particularly in the context of alcohol consumption and certain medications that affect the liver. GGT is an enzyme found in many tissues, especially the liver, and when liver cells are damaged, GGT is released into the bloodstream, causing elevated levels in blood tests. Doctors often order GGT tests alongside other liver enzymes like ALT, AST, and alkaline phosphatase to get a more complete picture of liver health. Elevated GGT levels may indicate conditions such as alcoholic liver disease, viral hepatitis, bile duct obstruction, fatty liver disease, or drug-induced liver injury. However, GGT isn't specific to any single condition, so elevated levels require further investigation to determine the exact cause.
Some of the key uses of GGT include:
- Evaluating liver function and detecting liver disease
- Monitoring treatment effectiveness and disease progression in patients with known liver conditions
- Detecting bile duct obstruction
- Identifying conditions such as alcoholic liver disease, viral hepatitis, and fatty liver disease
- Assessing the effectiveness of medications that affect the liver
According to the most recent study 1, GGT can help confirm whether an elevated alkaline phosphatase (ALP) level is of hepatic or nonhepatic origin. Concomitantly elevated GGT can indicate that an elevated ALP originates from the liver and suggests cholestasis. The study also notes that isolated elevated ALP of hepatic origin that persists over time may suggest a chronic cholestatic process.
It's worth noting that while GGT is a useful diagnostic tool, it is not specific to any single condition and should be used in conjunction with other tests and clinical evaluations to determine the underlying cause of elevated levels. As stated in the study 1, liver-related enzymes, including GGT, may suggest alcohol use but are inadequate to establish alcohol use in ALD on their own.
In terms of normal values, GGT levels typically range from 8 to 61 units per liter for men and 5 to 36 units per liter for women, though reference ranges may vary between laboratories 1. GGT levels can also be influenced by factors such as body mass index (BMI) and sex, as noted in the study 1.
Overall, GGT is a valuable diagnostic tool for evaluating liver function and detecting liver disease, and its use should be guided by the most recent and highest-quality evidence available.
From the Research
Uses of GGT
- GGT (Gamma-Glutamyl Transferase) is used as an index of liver dysfunction and a marker of alcohol intake 2
- It is also used to indicate liver injury and excessive alcohol consumption 3
- GGT has been linked to various chronic conditions and diseases, including nonalcoholic fatty liver disease, vascular and nonvascular diseases, and mortality outcomes 3
- It is used as a biomarker for oxidative stress associated with glutathione metabolism and as a proatherogenic marker due to its indirect relationship with low-density lipoprotein cholesterol oxidation 4
- GGT is used in combination with other markers to diagnose alcoholism in chronic liver diseases, with a high positive predictive value 5
Clinical Applications
- GGT is used to assess liver damage and disease, including obstructive liver disease, high alcohol consumption, and use of enzyme-inducing drugs 2
- It is used to evaluate the risk of coronary heart disease, Type 2 diabetes, and stroke 2
- GGT is used as a biomarker for cardiovascular risk evaluation, with high levels indicating an increased risk of cardiovascular events and all-cause mortality 4