From the Guidelines
GGT testing is effective for confirming whether elevated alkaline phosphatase (ALP) is of hepatic or nonhepatic origin, and it is a valuable diagnostic tool for monitoring liver function and detecting liver damage or disease. GGT is an enzyme primarily found in liver cells, and elevated levels in the blood indicate liver cell damage or biliary tract obstruction 1. The test is particularly useful for detecting alcohol-induced liver injury, as GGT levels rise after even moderate alcohol consumption and can remain elevated for up to 2-3 weeks following alcohol cessation.
Key Points to Consider
- Normal GGT values typically range from 0-30 IU/L for men and 0-24 IU/L for women, though reference ranges may vary between laboratories.
- GGT testing is often included in comprehensive liver panels alongside other tests like ALT, AST, and alkaline phosphatase to provide a more complete picture of liver health.
- While GGT is highly sensitive to liver damage, it lacks specificity as levels can also increase due to medications (like phenytoin and barbiturates), pancreatic disease, heart failure, kidney disease, and obesity 1.
- This makes GGT most valuable when interpreted alongside other liver function tests and clinical information.
- For monitoring liver health, GGT testing may be recommended every 3-6 months for patients with chronic liver conditions or those taking potentially hepatotoxic medications.
Clinical Application
- Concomitantly elevated GGT can help confirm that an elevated ALP originates from the liver and indicates cholestasis 1.
- If the liver is suspected to be the source of elevated ALP, together with a review of the patient’s clinical history and medications, imaging of the biliary tree may be necessary to determine the etiology of extrahepatic or intrahepatic cholestasis.
- A raised GGT is associated with increased liver as well as all-cause (including cancer) mortality, with the greatest risk being observed in those with the most significant elevations of GGT 1.
From the Research
Role of GGT Testing in Monitoring Liver Function
GGT testing is effective for monitoring liver function and detecting liver damage or disease, particularly in cases of hepatocellular injury and cholestatic injury.
- GGT levels are often used in conjunction with other liver function tests, such as alanine transaminase (ALT) and aspartate transaminase (AST), to assess liver health 2.
- Elevated GGT levels can indicate liver damage or disease, and can be used to guide further evaluation and treatment 3.
Detection of Liver Damage or Disease
GGT testing can be used to detect liver damage or disease, including:
- Non-alcoholic fatty liver disease (NAFLD) 2
- Alcoholic liver disease 3
- Viral hepatitis 3
- Primary biliary cholangitis and primary sclerosing cholangitis 3
- Hepatocellular disease or biliary obstruction 3
Effectiveness of GGT Testing
Studies have shown that GGT testing can be effective in reducing liver enzyme levels, including: