From the Guidelines
GGT is a crucial liver enzyme that indicates liver disease or bile duct problems when elevated, and its measurement is essential in conjunction with other liver tests like ALT, AST, and alkaline phosphatase to assess liver health and function. GGT, or gamma-glutamyl transferase, is involved in glutathione metabolism and helps move molecules across cell membranes. Elevated GGT levels can be caused by various conditions, including hepatitis, cirrhosis, bile duct obstruction, certain medications, and pancreatic disease 1.
Key Points to Consider
- Normal GGT values range from 8-61 units/L for men and 5-36 units/L for women, though these ranges may vary by laboratory.
- GGT is particularly sensitive to alcohol consumption, making it useful for detecting alcohol-related liver damage or monitoring alcohol abstinence 1.
- The measurement of GGT, along with other liver tests, is essential for early detection of liver disease, especially in patients with a history of alcohol consumption.
- GGT is not specific to any particular condition, so it is typically ordered alongside other liver tests to get a more complete picture of liver health and function.
Clinical Implications
- Elevated GGT levels can indicate liver disease or bile duct problems, and further testing may be necessary to determine the underlying cause.
- GGT can be used to monitor liver health in patients with a history of alcohol consumption or those taking medications that can affect the liver.
- The combination of GGT with other liver tests, such as ALT, AST, and alkaline phosphatase, can provide a more accurate assessment of liver health and function 1.
From the Research
Definition and Function of GGT
- Gamma-glutamyltransferase (GGT) is a liver enzyme located on the plasma membranes of most cells and organ tissues, particularly in hepatocytes 2.
- The primary role of GGT is the extracellular catabolism of glutathione, a major thiol antioxidant in mammalian cells, which protects cells against oxidants produced during normal metabolism 2, 3.
- GGT plays a crucial role in cellular defense and is involved in the breakdown of extracellular glutathione, making its component amino acids available to cells 3.
Clinical Applications and Associations
- Serum GGT is widely used as an index of liver dysfunction and a marker of alcohol intake 2, 3.
- Elevated GGT levels have been linked to various chronic conditions, including nonalcoholic fatty liver disease, vascular and nonvascular diseases, and mortality outcomes 2, 4.
- GGT is associated with the metabolic syndrome and is often elevated in patients with nonalcoholic fatty liver disease (NAFLD) 4, 5.
- High GGT levels are an independent predictor of risk for coronary heart disease, Type 2 diabetes, and stroke 3.
Prognostic Value and Risk Factors
- Frequently abnormal serum GGT activity is associated with an increased risk of developing fatty liver 5.
- Elevated GGT levels are a risk factor for fatty liver changes, and high triglyceride levels further increase this risk 5.
- Normalization of GGT levels is associated with better metabolic control in individuals with NAFLD, and weight loss is a significant predictor of GGT normalization 6.
- Good control of weight and insulin resistance is a reliable predictor of GGT normalization in NAFLD patients 6.