From the Guidelines
Gamma-glutamyl transferase (GGT) levels may range between low normal and >400 U/L, and the normal reference range is typically between 8-61 U/L for men and 5-36 U/L for women, though these values may vary slightly between laboratories. GGT is primarily used to assess liver function and detect bile duct obstruction. Elevated GGT levels often indicate liver disease, alcohol consumption, certain medications, or biliary tract disorders. When interpreting GGT results, it's essential to consider them alongside other liver enzymes like ALT, AST, and alkaline phosphatase for a comprehensive evaluation. GGT is particularly sensitive to alcohol use, making it valuable for detecting recent alcohol consumption and monitoring abstinence in patients with alcohol use disorders. If GGT levels are elevated, follow-up testing and evaluation of potential causes are recommended, which may include ultrasound imaging of the liver and biliary system, additional blood tests, or medication review.
- Key points to consider when evaluating GGT levels include:
- GGT levels can vary significantly between individuals and laboratories
- Elevated GGT levels do not necessarily indicate serious disease, but should prompt further investigation
- GGT is a sensitive marker for alcohol use and can be used to monitor abstinence in patients with alcohol use disorders
- GGT should be interpreted in conjunction with other liver enzymes and clinical evaluation to determine the underlying cause of elevation According to the most recent study 1, the upper limit of normal (ULN) for GGT is 20 U/L, and this value is used as a reference point for evaluating liver function and detecting potential liver injury. However, it's essential to note that the normal reference range for GGT can vary between laboratories, and the specific ULN value used may depend on the laboratory and the individual patient's characteristics.
From the Research
GGT Reference Range
The reference range for Gamma Glutamyl Transferase (GGT) is not explicitly stated in the provided studies. However, the studies discuss the importance of liver function tests, including GGT, in evaluating liver health and disease.
Liver Function Tests
- Liver function tests, including GGT, ALT, AST, and ALP, are essential in diagnosing and monitoring liver disease 2.
- The interpretation of these tests is crucial, and normal values do not necessarily rule out advanced chronic liver disease 2.
- Elevated levels of liver function tests do not automatically indicate liver failure 2.
GGT and Cardiovascular Mortality
- A systematic review and dose-response meta-analysis found a significant association between GGT levels and cardiovascular disease (CVD) mortality 3.
- The study found that high levels of GGT were associated with an increased risk of CVD mortality 3.
- The association between GGT and CVD mortality was found to be nonlinear, with higher levels of GGT corresponding to a greater risk of CVD mortality 3.
Clinical Implications
- Clinicians should consider the possibility of extrahepatic biliary obstruction, even when AST is the predominantly elevated enzyme 4.
- Elevated liver tests, including GGT, should be evaluated in the context of the patient's clinical presentation and medical history 5.
- A liver biopsy may be considered when serologic testing and imaging fail to elucidate a diagnosis, to stage a condition, or when multiple diagnoses are possible 5.