The big picture: Gamma-glutamyl transferase (GGT) is an enzyme primarily located in the liver, but it is also found in the kidneys, pancreas, and bile ducts. It is crucial for transporting amino acids into cells and supporting glutathione, a key antioxidant that protects cells from damage. GGT levels are commonly elevated due to obesity, excess alcohol consumption, or drug use.

GGT and liver health: GGT plays a vital role in liver function and is one of the best predictors of liver-related mortality. It aids in the metabolism of drugs and toxins by supporting the liver's detoxification pathways. Elevated GGT levels often indicate liver conditions such as hepatitis, cirrhosis, fatty liver disease, and bile duct obstructions. GGT is typically measured alongside other liver enzymes, like alanine aminotransferase (ALT) and aspartate aminotransferase (AST), for a comprehensive assessment of liver health.

Low specificity: GGT is very sensitive and can increase temporarily due to medications or recent alcohol consumption. Genetic differences can affect how GGT levels respond to alcohol, with even small amounts within 24 hours potentially causing a temporary rise. Smoking can also elevate GGT levels. If other liver enzymes are normal, it is advisable to repeat the GGT test later.

GGT’s role in bile production: In the bile ducts, GGT is involved in forming and transporting bile, which is essential for digesting and absorbing fats. Proper bile flow facilitated by GGT helps break down dietary fats into smaller molecules for absorption by the intestines. This process supports efficient nutrient absorption and waste elimination, maintaining overall digestive health.

Non-liver indications: While primarily associated with liver function, elevated GGT levels are linked to cardiovascular diseases like coronary heart disease, stroke, and arteriosclerosis due to its role in oxidative stress and inflammation. GGT can also indicate metabolic syndrome, which includes conditions like insulin resistance and hypertension. Additionally, high GGT levels are associated with increased risks of certain cancers, chronic kidney disease, and neurodegenerative conditions such as Alzheimer's disease.