Viral Hepatitis and Liver Disease Website Course

Evaluating Liver Test Abnormalities

Understanding the Pathophysiology of Liver Disease

for Health Care Providers


alanine aminotransferase (ALT)

Injury to hepatocytes causes ALT to leak out into the systemic circulation. ALT is more specific to the liver than AST.

aspartate aminotransaminases (AST)

Injury to hepatocytes causes AST to leak out into the systemic circulation. AST is not specific to the liver and can also be liberated during muscle injury.

cholestatic liver injury or cholestasis

Occurs when there is a disruption of bile flow (alkaline phosphatase/GGT and bilirubin levels are elevated with variable elevation of other liver enzymes). Severe injury can lead to dark urine, pruritus and jaundice.

hepatic sinusoids

Specialized capillary system of the liver. Unlike other capillary beds, hepatic sinusoids are leaky, allowing close contact between circulating blood and hepatocytes.


A condition where there is a disruption of bile flow. Cholestasis is classified as intrahepatic or extrahepatic


A reaction where a substrate was modified by addition of

direct bilirubin

Conjugated bilirubin. Results from glucuronidation of unconjugated bilirubin in the liver. It is water soluble and can therefore be excreted into bile.

indirect bilirubin

Unconjugated bilirubin. It is not water soluble and needs to be conjugated with glucuronide before being excreted into bile. Conjugation occurs in the liver.

bilirubin UDP

Product of heme degradation.

glucuronyl transferase (UDPG)

A hepatic enzyme catalyzing conjugation of glucorunide to bilirubin. Deficiency of this enzyme leads to direct hyperbilirubinemia


A genetic disease of iron metabolism, resulting in iron accumulaton and liver injury.