Liver Function Tests

Question 1

alanine aminotransferase (ALT) is found

Answer 1

hepatocyte cytoplasm, some in muscle

Question 2

aspartate transaminase (AST) is found

Answer 2

in hepatocyte cytoplasm and mitochondria

Question 3

lactate dehydrogenase is found

Answer 3

in the cytoplasm; high concentrations in muscle and liver

Question 4

alkaline phosphatase (ALP) is found

Answer 4

on the canalicular surface of hepatocytes and bone during formation

Question 5

gammaglutamyl transpeptidase (GGT) is found

Answer 5

canalicular surface of hepatocytes

Question 6

Liver necrosis releases which enzymes?

Answer 6

• AST (+toxins), ALT, LD
• due to virus, toxins, anoxia, paracetamol

Question 7

In biliary disease causing obstruction, what liver enzymes are released?

Answer 7

ALP & GGT (via lymphatics)

Question 8

Which liver enzymes are released in response to drugs (including alcohol)?

Answer 8

• not in response to damage
• increased production of ALT and GGT in response to alcohol, anticonvulsants

Question 9

Which enzyme is most liver specific?

Answer 9

ALT

Question 10

ALT catalyzes

Answer 10

pyruvate <–> alanine

Question 11

AST is involved in

Answer 11

• aspartate –> glutamate
• oxaloacetate and malate movement in/out of mitochondria

Question 12

Release of AST suggests

Answer 12

damage to cytosol and mitochondria of any cell containing them (liver, muscle, blood)

Question 13

Elevated ALT suggests

Answer 13

cytosolic damage, most likely in liver (less so in muscle, kidney)

Question 14

AST is removed

Answer 14

by the kidney, 2x as fast as ALT (18hrs)

Question 15

ALT is removed

Answer 15

by the liver, slower than AST (36hrs)

Question 16

If AST > ALT

Answer 16

• acute injury affecting cytoplasm and mitochondria
• eg alcohol, toxins

Question 17

If ALT > AST

Answer 17

• chronic or resolving injury
• AST has gone away but the ALT is accumulating
• eg hepatitis

Question 18

ALT levels in Hep A

Answer 18

• mild = 250
• moderate = 1000
• severe = 5000
• ALT > 10 000 = death

Question 19

Normal ALT is

Answer 19

<50 IU/L

Question 20

ALT in acute Hep B infection is

Answer 20

~2000-5000

(core positive IgM, current infection)

Question 21

ALT in chronic Hep B infection is

Answer 21

much lower than acute, ~50-250

(SA Ag positive, chronic infection)

Question 22

ALT levels in chronic hepatitis infections

Answer 22

are typically lower than in acute

Question 23

What types of drugs can cause hepatic damage?

Answer 23

• antibiotics
• statins
• ethanol
• paracetamol
• herbal tea/kombucha

Question 24

AST and ALT > 10x normal suggest

Answer 24

acute or severe insult:

drugs, acute viral hepatitis, CMV (glandular fever), hypoxia, splenomegaly

Question 25

ALT and AST \> 5x normal suggests

Answer 25

infection, alcohol, fatty liver disease, medications

Question 26

Elevated AST without elevation in ALT suggests

Answer 26

muscle and/or red cell damage eg statins causing muscle wasting (ie **mitochondrial damage in tissues other than liver**)

Question 27

Creatine kinase levels can be estimated by

Answer 27

AST x 20 normally \<200

Question 28

ALT elevated without an elevation in AST suggests

Answer 28

chronic or resolving disease eg Hep B, Hep C

Question 29

What happens to ALT and AST levels as the liver approaches cirrhosis?

Answer 29

they **decrease**; there are fewer hepatocytes left to damage and release ALT and AST

Question 30

Total protein is normally

Answer 30

60-80g/L

Question 31

normal albumin is

Answer 31

35-55g/L

Question 32

normal ALP is

Answer 32

\<120 IU/L

Question 33

normal bilirubin is

Answer 33

\<26mmol/L

Question 34

normal GGT is

Answer 34

\<50 IU/L

Question 35

normal AST is

Answer 35

\<45 IU/L

Question 36

Raised ALP is normal in

Answer 36

3rd trimester of pregnancy; produced by placenta

Question 37

Increased GGT suggests

Answer 37

biliary disease

Question 38

What is the function of GGT?

Answer 38

* transfers glutamyl groups to AA * helps transport of AA across membranes * **important in production of glutathione**

Question 39

What is the function of ALP?

Answer 39

* adds phosphate groups to things in membranes in alkaline environments

Question 40

In extra-hepatic biliary obstruction (cancer, stones), GGT and ALP

Answer 40

increase significantly, up to 20-30x normal levels

Question 41

In intra-hepatic biliary obstruction, GGT and ALP

Answer 41

will be mildly elevated, bilirubin should be normal can be due to tumours affecting small parts of liver or induction by drugs etc.

Question 42

Intrahepatic biliary obstruction can be due to

Answer 42

damage to a small part of the tree (tumour, lesion, etc.( or drugs inducing enzymes (alcohol, convulsants)

Question 43

What is the commonest cause of liver enzyme elevation?

Answer 43

obesity

Question 44

Which enzyme does BMI affect?

Answer 44

ALT; AST less-so because it can disappear, GGT affected more in the intermediate/pre-diabetic stage of obesity

Question 45

What causes fatty liver in obesity?

Answer 45

* fructose * from high fructose corn syrup * from sucrose (fructose + glucose)

Question 46

How does fructose cause fatty liver in obesity?

Answer 46

* only body tissue it can enter is liver * liver can convert fructose into glucose but not likely to do so because dietary glucose is sufficient * insulin response tells liver not to make glucose from fructose bc sugar is abundant in blood * fructose instead gets broken down into 3C units that are turned into fat