Liver Enzyme Basics

Question 1

ALT/AST

Answer 1

Located in hepatocytes; these leak with ongoing inflammation and injury

Marker of liver cell injury

Very high with viral, toxin, ischemia (>1,000)

Obese pts may be slightly higher than normal pts

ALT more specific to the liver than AST

Question 2

Alkaline phosphatase

Answer 2

Located in the hepatocyte membrane bordering bile canaliculi

Also in bone and placenta–can use iso enzymes to specify

Higher elevations from drugs, intra or extra hepatic obstruction

Lower levels from chronic liver disease

Question 3

Bilirubin

Answer 3

Water soluble product of heme metabolism

Unconjugated is poorly absorbed–>binds with albumin–>taken up by hepatocyte–>conjugated with glucoronic acid–>now water soluble and excreted through biliary system

Unconjugated (Indirect):

• Gilberts-lack of conjugation enzyme
• Hemolysis

Conjugated (direct)

• Liver dysfunction
• Obstruction

Question 4

Albumin

Answer 4

Measures synthetic function

Half life 20 days (doesn’t show up acutely)

Level affected by many factors–nutrition, liver synthesis, malabsorption, protein loss from GI or urinary system

Question 5

PT/INR

Answer 5

Coagulation factors II, V, VII, and X are synthesized in the liver

Measures liver ftn