Chemical Pathology 17 - EMQs on Enzymes, Chemistry

Question 1

Which enzymes is increased in a patient with Paget’s disease of the bone?

Answer 1

ALP and osteocalcin

Question 2

What is the pathophysiogy of Paget’s disease?

Answer 2

Increased osteoblast activity (increased osteocalcin)

Increased osteoclast activity

Question 3

features of Paget’s

Answer 3

Asymptomatic

Bowed tibia (it will also be warm)

High risk of fracture

Question 4

Which enzyme is increased in osteomalacia?

Answer 4

Lack of vitamin D → 2nd HPT → high PTH

High ALP due to increased bone turnover

Question 5

What type of technetium is used in bone scans vs thyroid scans?

Answer 5

Bone scans: Tc bisphosphonate - look for mets
Thyroid scans: Tc pertechnate

Question 6

What is the treatment for Pagets disease of the bone ?

Answer 6

bisphosphonates (only if painful) – bone formed with Ca2+ bisphosphonate not degraded by osteoclasts

Question 7

What is raised/low in primary HPT?

Answer 7

Calcium/vit D

vitamin D blood test measures levels of 25-(OH)cholecalciferol (calcidol) – i.e. pre-activation to calcitriol

PTH activates 1-alpha hydroxylase meaning that vitamin D is consumed (i.e. it is activated)

Question 8

What rises the most in acute renal failure?

Answer 8

urea - dehydration

Question 9

What rises the most in chronic renal failure?

Answer 9

creatinine - fall in GFR

Diabetes, as a cause of CKD, is much more rapidly progressive than other causes of renal impairment

With diabetes, if you have a creatinine >200 μmol/L, you are likely to reach end-stage renal failure within a year

Having a high creatinine does NOT mean that you need dialysis

Question 10

what is raised in rhabdomyolysis?

Answer 10

Creatinine kinase - muscle breakdown → renal failure (AKI)

Question 11

How can you prevent rhabdomyolysis ?

Answer 11

IV bicarbonate allows them to excrete extra CK

Question 12

What is a marker of glucose control over last 3 weeks?

Answer 12

fructosamine

It is important to have good diabetic control during pregnancy (cannot wait 3 months to assess HbA1c)

Question 13

Which one is increased in a patient following an acute myocardial infarction?

Answer 13

AST>CK>LDH

Troponins CK (MB) AST (important in gluconeogenesis) LDH

AST

• Increase following an acute MI (AST is found within the myocytes)
• AST goes up about 3 days after an MI and remains for around 14 days (3-14 days)

Question 14

Recall the timeline of elevation of troponin I, AST and LDH elevation post-MI

Answer 14

Troponin I - first few hours
AST - first day
LDH - over first 5 days

Question 15

What is raised in Addison’s disease?

Answer 15

potassium

Question 16

Which LFT result will be most deranged in obstructive jaundice?

Answer 16

ALP

Question 17

Which enzymes are most elevated by gallstones vs viral hepatitis and why?

Answer 17

Gallstones: ALP - stones tend to cause most damage near portal triad, where more ALP is made

Viral hepatitis - ALT - the virus tends to affect hepatocytes around the central vein the most, where ALT is predominantly produced

Question 18

Descrine the pathophysiology of alcoholic hepatitis causing portal hypertension

Answer 18

Alcoholic hepatitis –> hepatocyte death
The person becomes ill and recovers, and the hepatocytes regenerate. However, rather than regenerating as before, they form a NODULE
This nodule disrupts hepatic micro-architecture between the portal vein and the central vein
If enough nodules appear, this increases pressure in the portal vein –> portal HTN

Question 19

What enzyme is most raised in prostatic carcinoma?

Answer 19

acid phosphatase (PSA)

Question 20

Which one is most increased in a patient with jaundice caused by chronic alcoholic cirrhosis?

Answer 20

AST = destroyed liver architecture

Liver architecture is destroyed by repeated episodes of cell death followed by nodular regeneration.

Question 21

Which type of nuclear medicine test is most useful for identifying Ca cells themselves?

Answer 21

FDG-PET

Question 22

Which type of nuclear medicine test is most useful for identifying primary neuroendocrine tumours (eg insulinomas)?

Answer 22

Gallium 68 dotatate PET and CT (identifies somatostatin receptor)

Question 23

Which type of nuclear medicine test is most useful for parathyroid scans?

Answer 23

Sesta MIBI scan

Used by the parathyroids and myocardium

I.E. in MI, you see an area of a lack of uptake of MIBI

Question 24

Which type of nuclear medicine test is most useful for investigating for a phaeochromocytoma?

Answer 24

MIBG (looks for phaeo mets)

MIBG is a precursor for adrenaline that is used for identifying phaeochromocytoma

NOTE: Gallium dotatate picks up any neuroendocrine tumour (includes phaeochromocytoma and insulinomas)

Question 25

creatine kinase vs creatinine

Answer 25

CK → creatinine - Protein in your muscle and the waste produced by it is creatinine - People have a fixed muscle mass, you make creatinine at a fixed rate - Therefore, when the kidneys fail, the creatinine goes up

Question 26

WHat is FDG PET used for?

Answer 26

glucose uptake Non-specific marker as glucose is taken up by ANY active cell Cancer cells are more active so they will take up more FDG

Question 27

What is Gallium 68 DOTATATE PET + CT used for?

Answer 27

Nuclear Medicine localisation Gallium stuck onto somatostatin analogue → to tissues w/ somatostatin receptors; i.e. any neuroendocrine cell (none in brain, some in pituitary, many in spleen - always hot (also kidney, cysts in kidney and adrenals)