Gamma-glutamyl transferase (GGT) is an enzyme that is found in the body and the liver is the main source of GGT to the blood.
Normally, GGT is present in low levels, but when the liver is injured, the GGT level can rise. GGT is usually the first liver enzyme to rise in the blood when any of the bile ducts that carry bile from the liver to the intestine becomes obstructed, for example, by tumors or stones. This makes it the most sensitive liver enzyme test for detecting problems with the bile duct.
GGT levels are sometimes increased with consumption of even small amounts of alcohol. Higher levels are commonly found in chronic heavy drinkers or alcoholics. The GGT test may be used in evaluating someone for acute or chronic alcohol abuse.
What does the test result mean?
An elevated GGT level suggests that something is damaging the liver but it cannot specifically indicate what. In general, the higher the level, the greater the damage to the liver. Elevated levels may be due to liver diseases, such as hepatitis or cirrhosis, but they may also be due to other conditions, such as congestive heart failure, diabetes, or pancreatitis. They may also be caused by alcohol abuse or use of drugs that are toxic to the liver.
A low or normal GGT test result indicates that it is unlikely that a person has liver disease.
How to prevent elevated GGT levels
Even small amounts of alcohol within 24 hours of a GGT test may cause a temporary increase in the GGT. Smoking can also increase GGT. Elevated GGT levels may be an indicator of cardiovascular disease and/or hypertension.
Some studies have shown that people with increased GGT levels have an elevated risk of dying from heart disease, but the reason for this association is not yet known.
Drugs that may cause an elevated GGT level include phenytoin, carbamazepine, and barbiturates such as phenobarbital. Use of many other prescription and non-prescription drugs, including non-steroidal anti-inflammatory drugs (NSAIDs), lipid-lowering medications, antibiotics, histamine receptor blockers (used to treat excess stomach acid production), anti-fungal agents, antidepressants, and hormones such as testosterone, can increase GGT levels. Levels of GGT increase with age in women, but not in men, and are always somewhat higher in men than in women.