Liver Function Tests Flashcards
What enzymes that are tested for relate to the liver lobule?
AST and ALT
What enzymes that are tested for that are related to the bile duct/portal triad?
GGT and ALP
note also bilirubin
How is bilirubin metabolised by the liver?
- Haem is broken down, and bilirubin, attached to albumin heads to the liver (unconjugated bilirubin) (>85% of total in blood)
- In the liver, bilirubin is conjugated to become bilirubin glucuronide (
How does this change in something, for example haemolysis?
- Would be an increase in serum unconjugated bilirubin.
- As a result, increased urobilinogen, so more of it is lost on faeces, and some in urine also (brown urine)
How would hepatitis/cancer affect the metabolism?
increase in blood conjugated bilirubin (blockage of it leaving), so more in urine
What are the ways that jaundice can occur?
Unconjugated means: haemolysis, Gilberts syndrome
Conjugated means: cholestasis (drugs, preg., thyroid disease); liver obstruction (metastatic cancer, hepatitis, cirrhosis
Outside liver means: obstruction outside liver (gallstones, biliary/pancreatic cancer, pancreatitis)
What does ALP do, what is its variation and its main sources?
Alkaline phosphatase, transfers phosphate groups. Variation is wide and age related.
Main sources are liver (biliary system when inflammed or obstructed) and bone (osteoblasts)
What diseases can high ALP POTENTIALLY suggest?
Gallstones, prim. biliary cirrhosis, metastases.
What is GGT, what is its source, and what causes it to rise?
Gamma-Glutyl transferase, comes from liver mainly (also heart, pancreas).
Elevates due to inflmmation/obstruction of biliary system or is inducible by drugs or alcohol (alcohol espec.)
What is ALT, and where is it sourced from?
Alanine aminotransferase, conversion of alanine to pyruvate, found mainly in the cytosol of hepatocytes. Some in muscle
Is the most liver specific enzyme.
What is AST, and where is it sourced?
Aspartate transaminase, conversion of aspartate into oxaloacetate.
Sourced from the liver (cytosol and mitochondria), and in heart, muscle and red cells.
Less specific than ALT
Has a shorter half life than ALT (so will disappear quicker than ALT)
What do high: ALT and AST levels signify?
ALT: hepatitis
AST: early hepatitis
What do albumin levels fall with?
Decreased synthesis (cirrhosis)
increased loss (in kidneys)
illness
redistribution
Overall if liver is worsening, decreased albumin unless sudden onset
What do globulins, prothrombin and glucose levels reflect?
Globulins-high during inflammtion, very high when chronic
Prothrombin ratio- higher number means less clotting factors, and arise also indicates low vit. K
glucose- liver maintains fasting glucose so an inability to maintain
What is CEA?
carcinoembryonic antigen, when above 20, almost always a malignant cancer, and is higher in smokers
