Which liver enzymes are affected by hepatitis?

From the Guidelines

Hepatitis primarily affects liver enzymes known as aminotransferases, specifically alanine transaminase (ALT) and aspartate transaminase (AST), as evidenced by the most recent study on abnormal liver function tests 1. The elevation of these enzymes occurs because inflammation damages liver cells, causing them to release their contents into the bloodstream.

• ALT elevations are specific for liver injury owing to low concentrations in skeletal muscle and kidney, with normal levels ranging from 19 to 33 IU/L depending on gender 1.
• AST elevations, on the other hand, can be due to disorders involving other organs such as the heart, skeletal muscle, kidneys, brain, and red blood cells, in addition to liver damage 1. Other liver enzymes that may be affected include alkaline phosphatase (ALP), which may be elevated in cholestatic liver disease, and bilirubin, which often increases in hepatitis, causing jaundice when significantly elevated 1. The pattern and degree of enzyme elevation can help differentiate between various types of hepatitis and assess disease severity, with the severity of abnormal aminotransferase classified as mild, moderate, or severe based on the upper reference limit 1.
• Mild elevations are less than 5 times the upper reference limit,
• Moderate elevations are 5 to 10 times the upper reference limit, and
• Severe elevations are more than 10 times the upper reference limit, with moderate and severe categories often discussed collectively due to significant clinical overlap 1.

From the Research

Liver Enzymes Affected by Hepatitis

• The liver enzymes most commonly affected by hepatitis are:
  • Alanine aminotransferase (ALT) 2, 3, 4, 5, 6
  • Aspartate aminotransferase (AST) 2, 3, 4, 5, 6
  • Alkaline phosphatase (ALP) 2, 5, 6
  • Gamma-glutamyl transferase (γ-GT) 2, 5

Hepatitis-Related Liver Damage

• Hepatitis can cause hepatocellular damage, leading to elevated levels of ALT and AST 2, 3, 4, 6
• The ratio of AST to ALT can help differentiate between alcoholic and non-alcoholic liver disease 2
• Elevated levels of ALP and γ-GT can indicate cholestasis, but these enzymes are not liver-specific and can be influenced by other factors such as alcohol and certain drugs 2, 5

Diagnostic Considerations

• A hepatic enzyme pattern (elevated transaminases) should be distinguished from a cholestatic pattern (elevated ALP and γ-GT) 2
• The presence of an elevated ALT has been associated with increased liver-related mortality 6
• The evaluation of hepatocellular injury includes testing for viral hepatitis, non-alcoholic fatty liver disease, and other conditions 6