Liver Function Tests

Question 1

what are transaminases

Answer 1

intracellular enzymes in the liver

Question 2

how are transaminases relseased

Answer 2

released from liver in context of hepatocellular injury

Question 3

types of transaminases

Answer 3

catalyse gamma-amino group transfers
alanine aminotransferase (ALT)
aspartate aminotransferase (AST)

Question 4

examples of catalyse gamma-amino group transfers

Answer 4

aspartate

alanine -> ketoglutarate

Question 5

describe ALT

Answer 5

more sensitive than AST

short half life circa 47 hours

Question 6

where is ALT located

Answer 6

cytosol in the liver

Question 7

where is AST located

Answer 7

cytosol and mitochondria in;

liver, heart, pancreas, skeletal muscle, brain, lungs, RBCs, WBCs

Question 8

describe when aminotranferases would be raised

Answer 8

become deranged in aetiologies - increase in hepatocellular pathologies
levels may/may not reflect the extent of damage

Question 9

levels of aminotransferases in obstructive jaundice

Answer 9

less than 500 U/L

Question 10

what are alkaline phosphatase

Answer 10

enzymes that catalyse the hydrolysis of a number of organic phosphate esters

Question 11

how are alkaline phosphatases raised

Answer 11

long half life and so therefore often lag to rise and slow precipitation in resolution of pathology

Question 12

where are alkaline phosphatase found

Answer 12

biliary (epithelial cells of ducts) cholestasis enhances synthesis and release of ALP
bone
placenta
intestine
kidney

Question 13

what are gamma glutamyl transpeptidases (GGT)

Answer 13

enzyme involved in gluthionine metabolsim, transfer of amino acids across cellular membranes and leukotriene metabolism

Question 14

where are GGTs located

Answer 14

cell membranes of;
liver
kidneys
bile duct
pancreas
gallbladder
spleen
heart
brain
seminal vesicle

Question 15

what does raised GGT indicate

Answer 15

diagnostic marker for liver or cholestatic diseases

determines whether elevated ALP is of bone or liver origin

Question 16

what may cause GGT to rise

Answer 16

consumption of alcohol

liver diseases

Question 17

describe unconjugated bilirubin

Answer 17

transported to liver bound to albumin

Question 18

describe conjugated bilirubin

Answer 18

bilirubin becomes water soluble and so is excreted in urine and faeces

Question 19

what clotting factors does the liver synthesise

Answer 19

factor; 
I (fibrinogen)
II (prothrombin)
V
VII
IX
X
XII
XIII

Question 20

what does prothrombin measure

Answer 20

the conversion time from PT to thrombin and thus reflects a vital component of the liver

Question 21

why would prothrombin be elevated

Answer 21

reduced synthetic functionality 
drugs (warfarin)
bilie malabsorption causing relative Vitmain K deficiency 
consumptive coagulopathies 
congenital coagulopathy

Question 22

patterns of hepatocellular injury

Answer 22

ALT/AST > ALP

increase bilirubin

Question 23

patterns of cholestasis

Answer 23

ALP > ALT/AST

increased bilirubin

Question 24

patterns of prolonged jaundice/vitamin K, malabsorption and hepatocellular dysfunction

Answer 24

increased prothrombin time

increased INR

Question 25

what enzyme is difficult to use in isolation

Answer 25

albumin