Liver Function Tests Flashcards
List the 4 main functions of the liver
Protein metabolism
CHO metabolism
Lipid metabolism
Detoxification and excretion
What are the 8 LFTs commonly provided by labs in Aus?
Protein Albumin Bilirubin ALT AST GGT ALP LD
What are the 6 main liver proteins?
Albumin a1-antitrypsin a2-macroglobulin Haptoglobin B-lipoprotein Transferrin
Which liver enzymes are predominantly cytoplasmic?
ALT
AST
LD
Which liver enzymes are nuclear?
DNA synthase
Which liver enzymes are located on the membrane?
ALP
GGT
Which liver enzymes are associated with organelles?
Mitochondrial AST
Lysosomal SOD
What liver enzymes rise in liver necrosis?
ALT
AST
LD
Which liver enzyme is particularly elevated in toxin-mediated liver necrosis? Why?
AST
Also damages organelles causing further release of AST
Which liver enzymes rise in biliary disease?
ALP
GGT
Give 2 examples of drugs which induce certain liver enzymes
Alcohol
Anticonvulsants
Which liver enzymes are typically elevated with inducing drugs?
ALP
GGT
What is the role of ALT?
Converts alanine to pyruvate which can then be converted to glucose (part of gluconeogenesis)
What is the role of AST?
Important in Krebs cycle (involved in transporting oxaloacetate from the cytoplasm into the mitochondria)
Is ALT or AST liver-specific?
ALT (L for liver-specific)
Which has a longer half-life: AST or ALT? What are the clinical implications?
ALT (L for longer, S for shorter)
AST > ALT suggests acute process affecting mitochondria (e.g. toxins)
ALT > AST suggests chronic/resolving process (e.g. hepatitis)
Which has the longest half-life: ALT, AST or GGT?
GGT (5-7 days)
List 4 viruses (other than viral hepatitis) that can cause hepatitis
EBV
CMV
Q fever
Rubella
Define a mild, moderate and severe ALT level
Mild: 250
Moderate: 1000
Severe: 5000
What pattern of ALT is seen in chronic viral hepatitis?
Intermittent rises as virus tries to “break out” of liver to infect further
What levels are generally seen in acute vs chronic hepatitis B/C?
Acute: can be around 5000
Chronic: 50-250
List 6 medications/herbs that can cause liver damage
Flucloxacillin Amoxicillin Statins (atorva, simvi, prava, fluva) Ethanol Paracetamol Herbal tea (kombucha)
Where is ALP found?
Liver
Bone
Placenta
Where is GGT found?
Liver
Biliary epithelium
Some renal
What is GGT involved in?
Glutathione metabolic pathway (antioxidant pathway)
What are the clinical features of extra- vs intra-hepatic cholestasis?
Extra: elevated conjugated bilirubin, markedly elevated GGT and ALP
Intra: no jaundice, normal bilirubin, mildly elevated GGT and ALP
What is a very poor sign in a pt with suspected cancer?
Very low albumin
What is Gilbert’s syndrome?
Mutation in promoter region of UDP glucuronosyltransferase (7 vs 6 normal repeats)
What is bilirubin a predictor of? Describe the relationship. What is hypothesised to be the underlying reason for this relationship?
Cardiac disease
The higher the bilirubin, the lower the risk of cardiac events
Bilirubin is a physiological antioxidant which protects the myocardium and prevents LDL being oxidated
What is the effect of fasting in a pt with Gilbert’s disease?
Bilirubin rises as body is metabolically stressed
What is the effect of weight on liver enzymes?
Increased ALT
List 8 determinants of raised ALT
Younger men Ethnicity BMI WHR Serum leptin Serum triglycerides Serum insulin Plasma glucose
What initial tests are recommended in suspected liver disease?
Serology
Iron studies
Glucose and lipids
List 4 second line liver tests
HFE gene
AutoAbs
a1-antitrypsin assay
Urine copper
What are some of the drawbacks of LFTs?
Little prognostic value
Little value for monitoring effect of therapy
Do not assess liver “function” quantitatively or dynamically (more accurately liver damage tests)
