Liver Function Tests

Question 1

Two enzymes that are markers for LIVER CELL NECROSIS

Answer 1

1. Serum Alanine Transaminase (ALT)- ONLY in LIVER
2. Serum Aspartate Transaminase (AST)

Question 2

Where is ALT found?

In what part of the cell?

What does it indicate?

Answer 2

ONLY in the liver

It is only present in the CYTOSOL of HEPATOCYTES

it is SPECIFIC for LIVER CELL NECROSIS

ALT>AST= viral hepatitis

Question 3

Where is AST located?

Is it specific for liver damage?

Elevated AST indicates what?

Answer 3

Present in the MITOCHONDRIA

It is NOT only found in the liver.

AST>ALT indicates alcoholic hepatocyte injury

Alcohol uncouples oxidative phosphorylation in the mitochondria & damages the mitochondria. Elevated AST can indicate fatty change of the liver, alcoholic hepatitis, or cirrhosis.

Question 4

What 2 enzymes are elevated in cholestasis (Obstruction of the bile duct)

Answer 4

1. Serum y-glutamyltransferase (GGT)
2. Serum Alkaline Phosphatase (ALP)

Question 5

Where is GGT found?

What does elevated GGT indicate?

Answer 5

ONLY in the SMOOTH ER of the LIVER

Elevation indicates Intra or Extrahepatic Obstruction to Bile Flow

Since it’s produced in the smooth ER of the liver, any induction of cytochrome P-450 system (ie drugs, alcohol) will increase GGT

Question 6

Where is Serum Alkaline Phosphatase (ALP) found?

What does it’s elevation indicate?

Answer 6

It is found in the liver as well as other organs.

Elevation can indicate increased osteoblastic activity in the bone.

ALP is also found in the placenta

Normal GGT with increased ALP indicates a source of ALP that is NOT the liver

Increased GGT AND ALP indicates CHOLESTASIS

Question 7

What does hyperbilirubinemia with a Conjugated Bilirubin <20% indicate?

Answer 7

UNCONJUGATED HYPERBILIRUBINEMIA

Question 8

What does Unconjugated Hyperbilirubinemia (CB<20%) indicate?

Answer 8

EXTRAVASCULAR HEMOLYSIS

Ex:

Spherocytosis

Rh & ABO HDN

warm AIHA

Question 9

What are the lab findings in jaundice caused by extravascular hemolysis?

CB? Urine Bilirubin? Urine UBG?

What type of hyperbilirubinemia does extravascular hemolysis cause?

Answer 9

Extravascular hemolysis causes increased production of mostly Unconjugated Bilirubin

CB<20%

Increased urine UBG

Absent Urine Bilirubin (unconjugated bilirubin in water insoluble)