Clinical Biochemistry Tutorial - Quiz Questions

Question 1

Clinical Case 1

• What is the disease?
• What is the most likely cause?

Answer 1

Primary hyperthyroidism:

• High T4; feeds back to supress TSH
• High T3; T4 converted to T3 in peripheries
• Low TSH

Most likely cause: Grave’s disease

Question 2

What is Grave’s disease?

Answer 2

An autoimmune condition associated with the formation of antibodies, which bind to and activate the TSH receptors in the thyroid gland.

Question 3

What is the most likely immediate treatment for thyrotoxicosis / Grave’s?

Answer 3

Beta-blockers and carbimazole; helps symptoms and starts to treat underlying cause.

N.B. 1-4 are treatments that are increasing in severity.

Question 4

Function of beta-blockers in hyperthyroidism?

Answer 4

Beta blockers ameliorate the symptoms of hyperthyroidism that are caused by increased beta-adrenergic tone. These include palpitations, tachycardia, tremulousness, anxiety, and heat intolerance by affecting the way thyroid hormone acts on your body.

These medications don’t change the amount of thyroid hormone in your body, but they can help you feel better by controlling your symptoms.

Question 5

Function of Carbimazole in hyperthyroidism?

Answer 5

Carbimazole is used to reduce the formation of thyroid hormones.

Question 6

Clinical Case 1 Continued

Answer 6

Compliant but TSH is in the natural lag phase; patient clinically feeling better

Question 7

Why are TFTs not usually repeated before 4-6 weeks?

Answer 7

Natural lag for changes to occur and thyroid to settle

Question 8

Clinical Case 2

• What is the disease?
• What is the most likely cause?

Answer 8

• Low free T4 & high TSH –> primary hypothyroidism
• Most likely cause –> Hashimoto’s Disease

Question 9

What is Hashimoto’s Thyroiditis? Treatment?

Answer 9

Hashimoto’s disease is an autoimmune disorder that can cause hypothyroidism. Treatment is thyroxine.

Question 10

Clinical Case 2 Continued (Hashimoto’s)

Answer 10

• T4 increase is a result of medication; shows patient is compliant
• TSH in normal range; adequately treated

Question 11

Clinical Case 3

• What is disease?

Answer 11

• Check for immunoassay interference!
• Low T4 but normal TSH –> secondary hypothyroidism
  
  • Pituitary is not stimulating thyroid
    
    • (with a malignant thyroid nodule; high T4 and low TSH suspected)

Question 12

Clinical Case 3 Continued: 2ary Hypothyroidism

Answer 12

1:

• Prolactin; to judge pituitary function
• 9 AM cortisol; cortisol peaks at this time (random cortisol unhelpful)
• LH/FSH/Oestradiol; hypothalamic-pituitary-gonadal axis for females
• MRI Pituitary Fossa; where lesion likely to be

Question 13

Clinical Case 3 Continued: 2ary hypothyroidism

Answer 13

• Compliant –> patient feeling better
• T4 levels good (in upper 2/3s of range) –> adequately treated
• TSH cannot give any indication as pituitary is not functioning

Question 14

Clinical Case 4

Part 1:

A 60 year old male is found to have raised blood sugar. Which endocrine cause is the least likely?

a) diabetes
b) acromegaly
c) Cushing’s
d) Addison’s disease

Part 2:

Upon further examination the clinician noted purple abdominal striae and moon face, from the list above which diagnosis is now most likely?

Answer 14

Part 1

• DM likely
• Acromegaly and Cushing’s syndrome likely –> cortisol and GH both act to increase blood glucose levels
• Addison’s disease
  
  • ​This is underfunction of adrenal gland so unlikely to be producing enough cortisol –> least likely to cause raised blood sugar

Part 2

• Cushing’s syndrome

Question 15

What initial screening test is used to investigate Cushing’s syndrome? What would the results show?

Answer 15

• 24 hour urine inaccurate, also cortisol unlikely to be normal
• Random cortisol unhelpful due to diurnal rhythm (and other triggers e.g. stress)
• Overnight dexamethasone test - cortisol 89 is the correct answer

Question 16

What is the least likely cause of Cushing’s syndrome?

a) exogenous steroids?
b) pituitary tumour?
c) adrenal tumour?
d) obesity?

Answer 16

• Exogenous steroids are likely (e.g. overtreatment with steroids is common)
• Pituitary tumour can secrete ACTH - is likely
• Adrenal tumour can secrete cortisol - is likely
• Obesity is least likely (but still can happen)

Question 17

Clinical Case 5

• What is the next most important test to determine underlying cause?

Answer 17

• High calcium tends to lead to renal stones
• Underlying cause likely to be:
  
  • Malignancy
  • Primary hyperparathyroidism
• PTH measurement is most useful

Question 18

Clinical Case 5 Continued: renal stones

What is the most likely diagnosis cause?

Answer 18

Primary hyperparathyroidism

Question 19

Clinical Case 6

Answer 19

• Repeat HbA1c; he has a Hb variant which reduces the normal life cycle of a red cell so not give an accurate reflection of glucose level over past 2-3 months
• Fructosamine; monitors only, not approved for diagnosis
• Glucose; only fasting plasma glucose has been certified for diagnosis (this glucose does not state if its fasting or random)
• Oral glucose tolerance test