Liver Function Tests

Question 1

explain why gynecomastia is seen in patients with chronic cirrhosis

Answer 1

• liver’s ability to degrade testosterone decreases, which leads to increased conversion of testosterone into estrogen by aromatase

Question 2

describe what serum bilirubin levels are in hepatitis

Answer 2

• liver conjugated bilirubin with glucuronic acid to form conjugated bilirubin that is excreted into the intestine
• in patients with hepatitis, serum total, conjugated and unconjugated bilirubin are increased
  
  • unconjugated increased because damaged liver has lower capacity for uptake and conjugation of bilirubin
  • conjugated bilirubin elevated in hepatitis due to inflammation

Question 3

describe serum bilirubin levels in cholestatic disease and how it changes in prolonged cholestsis

Answer 3

• serum conjugated bilirubin is predominantly elevated
  
  • urine is darker colored because conjugated bilirubin is being excreted into the urine
• serum unconjugated bilirubin may also be elevated in prolonged cholestasis, since liver cells become damaged over time

Question 4

contrast intrahepatic vs extrahepatic cholestasis

Answer 4

• intra-hepatic cholestasis is observed in viral hepatitis and drug toxicity and chronic cirrhosis
• extra-hepatic cholestasis is observed in:
  
  • stone in the common bile duct or gallbladder
  • tumors around the common bile duct or head of pancreas

Question 5

describe enzyme levels in hepatocellular injury

Answer 5

• raised ALT levels is more specific for acute liver cell damage compared to raised AST
  
  • in acute hepatitis, ALT levels >>>> AST levels
• in long standing alcoholic cirrhosis, AST >>>> ALT (2:1)

Question 6

which enzymes indicate cholestasis?

Answer 6

• ALP and GGT

Question 7

which enzymes are elevated in biliary stasis (intra or extra hepatic cholestasis)?

Answer 7

ALP and GGT

Question 8

What does an elevation in ALP with no increase in GGT indicate?

Answer 8

• bone disease, placental ALP

Question 9

what does an elevation in GGT and no increase in ALP indicate?

Answer 9

• only GGT increased is indicative of recent alcohol use or ingestion of drugs that induce GGT synthesis

Question 10

how does an ultrasound assess the biliary tree?

Answer 10

• if the biliary tree is dilated, then there is extrahepatic cholestasis
• if the biliary tree is not dilated, then intrahepatic cholestasis is suspected

Question 11

explain why there is an increased prothrombin time in patients with cholestasis

Answer 11

• cholestasis results in impaired absorption of fat soluble vitamins, including vitamin K, due to reduced entry of bile acids into intestine
• decreased absorption of vtamin K impairs the post-translational carboxylation of vitamin K dependent clotting factors (II, VII, IX, X) resulting in increased prothrombin time