The liver, one of the most important organs, has many metabolic and regulatory roles in the body including the processing of all things ingested, eliminating wastes and filtering the blood. In order to perform these tasks, proteins called enzymes are needed to help speed up reactions. Liver enzymes participate in metabolism, storage, filtration and excretion. If the liver becomes injured or diseased, however, liver cells may leak enzymes into the bloodstream, resulting in elevated liver enzyme tests.
Types
Liver enzymes most commonly measured are alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT). ALT and AST are made in the liver where they participate in the metabolizing of amino acids and the production of proteins. ALT is found in the liver only, whereas AST is found in the liver and other organs. ALP is found in the bones, intestines, placenta, kidneys and the liver. ALP is responsible for the production of energy and the metabolism of phosphorus. GGT is exclusively found in the liver and helps with the delivery of oxygen to body tissues.
Testing
Liver enzymes are measured with a simple blood test. Because certain foods or medications may affect test results, a physician may require fasting or the avoidance of certain medications immediately before the test.
Healthy Liver Enzyme Levels
Depending on the laboratory and the age and sex of the individual, normal liver enzyme levels may vary slightly. According to the Mayo Clinic, normal liver enzymes range within the following numbers: ALT 7 to 55 units per liter (U/L), AST 8 to 48 U/L, ALP 45 to 115 U/L and GGT 9 to 48 U/L.)
Elevated Levels
High ALT and AST numbers can indicate various issues including viral hepatitis, excessive alcohol intake, liver inflammation from herbs or medications, auto-immune hepatitis, fatty liver, liver tumors, inherited liver disease and heart failure. High levels of ALP can signify liver trouble if GGT levels are also elevated. GGT levels can rise above normal ranges from obesity, heavy drinking, fatty liver and medications or herbs that are toxic to the liver. Additionally, ALP and GGT are known as cholestatic liver enzymes. Cholestastis is the partial or full blockage of the bile duct. If the bile duct is inflamed or damaged, GGT and ALP will spill out into the blood stream.
Maintaining a Healthy Liver
The United States Department of Veterans Affairs has listed the following suggestions for maintaining a healthy liver: practice safe sex, do not inject drugs, eliminate or reduce alcohol consumption, do not share personal items that may have blood on them such as toothbrushes or razors, consider getting vaccinated for hepatitis A and B, follow food safety guidelines, maintain a healthy body weight, control blood sugars if diabetic, keep cholesterol and blood lipids within the normal range and inform your physician of all medications, supplements and herbs taken.
References
- "Anatomy & Physiology"; Elaine N. Marieb; 2005
- Liverenzymes.net: Liver Enzymes
- Mayo Clinic: Elevated Liver Enzymes
- Mayo Clinic: Liver Function Tests
- Aids Treatment Data Network: Liver Function Tests
