Gamma-Glutamyl Transferase, or GGT, is an enzyme present in cells throughout the body. While GGT is found in many organs, including the kidneys and pancreas, its highest concentrations are located in the liver. The primary role of GGT involves the transport of molecules across cell membranes. It plays a part in the breakdown and recycling of a compound called glutathione, which is involved in protecting cells from damage. Because of its high concentration in the liver, GGT’s presence in the bloodstream is linked to the health of this organ.
The Purpose of a Gamma-Glutamyl Transferase Test
A physician may order a GGT test for several reasons, primarily to investigate the possibility of liver or bile duct conditions. The test is often prompted by symptoms that suggest liver distress, including persistent fatigue, nausea, abdominal pain or swelling, and jaundice. Another common reason to measure GGT is to help determine the origin of a different elevated enzyme, alkaline phosphatase (ALP). While both GGT and ALP can be high in liver disease, only ALP is elevated in bone disorders, making the GGT test a useful tool for differentiation.
This blood test is also a sensitive marker for alcohol consumption and may be used to screen for chronic or heavy alcohol use. The test itself is a simple blood draw that requires minimal preparation.
Interpreting Elevated GGT Levels
An elevated GGT level in the blood indicates that the enzyme may be leaking from liver cells, but it is a sensitive yet non-specific signal that prompts further investigation. Generally, the higher the GGT level, the more significant the damage to the liver is considered to be. One of the most common reasons for high GGT is liver disease. Conditions such as viral or autoimmune hepatitis, cirrhosis, and non-alcoholic fatty liver disease (NAFLD) are also strongly associated with elevated GGT levels. These conditions disrupt normal liver cell function and integrity, allowing the enzyme to escape into the bloodstream.
Issues within the bile ducts are another major cause of increased GGT. If these ducts become blocked or damaged, a condition known as cholestasis, it prevents the normal flow of bile, which can cause GGT levels to rise significantly. Chronic alcohol consumption is a well-documented factor that raises GGT levels. The enzyme is highly sensitive to the effects of alcohol, and levels are frequently higher in individuals who drink heavily and regularly.
Other Factors That Can Influence GGT Results
Beyond primary liver disease and alcohol use, other factors can lead to an increase in GGT levels. Certain medications, both prescription and over-the-counter, are known to affect the liver and can cause GGT to rise. These can include some nonsteroidal anti-inflammatory drugs (NSAIDs), lipid-lowering drugs known as statins, certain antibiotics, and anticonvulsants. The elevation is often a side effect of the liver processing these substances.
Other medical conditions not directly related to the liver can also cause a moderate increase in GGT. Congestive heart failure, for example, can lead to liver congestion and subsequent enzyme elevation. Similarly, conditions like diabetes and pancreatitis have been associated with higher GGT levels. GGT levels can be influenced by factors such as age and gender, with levels being higher in adult males than females. Conversely, having low or normal GGT levels is not a cause for clinical concern and indicates the liver is not experiencing significant damage or stress.
Next Steps and Related Diagnostic Tests
Receiving a high GGT result is not a diagnosis in itself; it is an indicator that requires further evaluation. A healthcare provider will interpret the GGT level in the context of a patient’s symptoms, medical history, and other test results, often as part of a comprehensive liver function panel. To get a more complete picture of liver health, doctors will look at other liver enzymes and substances, including:
- Alanine transaminase (ALT)
- Aspartate aminotransferase (AST)
- Bilirubin
- Alkaline phosphatase (ALP)
Imaging tests may also be ordered as a follow-up. An ultrasound of the abdomen is a common next step to visualize the liver and bile ducts, checking for blockages, tumors, or signs of fatty liver disease. Discussing the results with a provider is necessary to determine the underlying issue and the most appropriate management plan.