Liver or Muscle?

If a primary disorder hasn't yet been diagnosed, a doctor may be misled into thinking that a damaged liver, not damaged muscles, is the source of the enzyme leak. In the general population, liver damage is more common than muscle damage. Of course, the careful physician will investigate further. There are some diagnostic tools which could help the doctor in differential diagnosis and they are also based on enzymes!

Differential diagnosis

• An enzyme called GGT or gamma-GT (gamma-glutamyltransferase) is found in the liver but not in the muscles.   
• Enzyme CK (creatine kinase), also called CPK (creatine phosphokinase), is only found in the heart, skeletal muscles and brain, but not in the liver.
• The MM form of CK is the type found in skeletal muscles, and it can be specifically measured when a doctor suspects a muscle problem

Liver enzymes

There are exactly 4 separate liver enzymes included on most routine laboratory tests. They are:

• aspartate aminotransferase (AST or SGOT)
• alanine aminotransferase (ALT or SGPT)
• alkaline phosphatase (AP)
• gamma-glutamyl transferase (GGT)

Common causes of elevated liver enzymes include:

• Medications, such as certain nonsteroidal anti-inflammatory drugs, cholesterol-lowering medications, antibiotics and anti-seizure medications
• Drinking too much alcohol
• Obesity
• Diabetes
• Elevated triglycerides
• Infection, such as viral hepatitis and mononucleosis
• Autoimmune disorders of the liver and bile ducts: autoimmune hepatitis (formerly chronic active hepatitis), primary biliary cirrhosis, sclerosing cholangitis
• Metabolic liver disease, such as hemochromatosis and Wilson's disease
• Excessive use of vitamin supplements and certain herbal supplements
• Tumors of the liver or bile ducts