From the Guidelines
Elevated levels of Gamma-Glutamyl Transferase (GGT) and Alanine Transaminase (ALT) are indicative of liver damage or disease, and it is crucial to investigate the underlying cause to prevent further liver injury and improve outcomes. These enzymes are primarily found in liver cells, and when these cells are damaged, the enzymes leak into the bloodstream, resulting in higher blood levels. GGT is particularly sensitive to alcohol consumption and certain medications, while ALT is more specific to liver cell damage 1. Common causes include alcoholic liver disease, viral hepatitis, non-alcoholic fatty liver disease, medication-induced liver injury, and biliary obstruction.
Key Considerations
- The pattern and degree of elevation can help determine the underlying cause. For instance, a GGT elevation with normal ALT might suggest alcohol use, while significant ALT elevation often indicates acute hepatocellular injury 1.
- If you have elevated levels, it's essential to avoid alcohol, review medications with your doctor, maintain a healthy weight, and follow up with additional testing as recommended.
- These may include ultrasound, viral hepatitis testing, or other liver function tests to determine the specific cause and appropriate treatment.
Important Factors
- The sensitivity for detection of daily ethanol consumption >50 g of CDT (69%), and GGT (73%) are higher than those of AST (50%), ALT (35%), and MCV (52%) 1.
- The specificity of CDT was 92%, compared with 75%, 82%, 86%, and 85% for GGT, AST, ALT, and MCV, respectively 1.
- GGT is usually higher in ALD patients compared with those who have other liver diseases, but serum GGT activity loses its specificity for alcohol in more advanced liver disease because its activity is elevated in patients with extensive fibrosis regardless of the cause 1.
From the Research
Significance of Elevated GGT and ALT Levels
Elevated Gamma-Glutamyl Transferase (GGT) and Alanine Transaminase (ALT) levels are markers of liver injury, but may also be associated with other diseases and death 2. The primary role of GGT is the extracellular catabolism of glutathione, which plays a relevant role in protecting cells against oxidants produced during normal metabolism 3.
Association with Mortality and Diseases
- Elevated GGT is associated with mortality from all causes, liver disease, cancer, and diabetes 2.
- ALT elevation is associated with deaths from liver disease, but not from cardiovascular disease, neoplasms, or diabetes 2.
- Serum GGT levels within the normal range predict the incidence of chronic elevation of ALT, suggesting a relationship between GGT and oxidative stress 4.
- High serum GGT is associated with higher mortality, partly due to its association with other risk factors and partly because GGT is an independent predictor of risk 5.
Clinical Applications
- GGT is used as an index of liver dysfunction and marker of alcohol intake 5.
- Serum GGT can be used to identify patients with primary biliary cholangitis (PBC) at risk for liver transplantation or death 6.
- Including information on GGT levels increases the prognostic value of the Globe score, a scoring system used to predict outcomes in patients with PBC 6.