Clinical Biochemistry Tutorial - Quiz Questions Flashcards

1
Q

Clinical Case 1

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

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

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2
Q

What is Grave’s disease?

A

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

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3
Q

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

A

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

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

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4
Q

Function of beta-blockers in hyperthyroidism?

A

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.

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5
Q

Function of Carbimazole in hyperthyroidism?

A

Carbimazole is used to reduce the formation of thyroid hormones.

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6
Q

Clinical Case 1 Continued

A

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

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7
Q

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

A

Natural lag for changes to occur and thyroid to settle

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8
Q

Clinical Case 2

  • What is the disease?
  • What is the most likely cause?
A
  • Low free T4 & high TSH –> primary hypothyroidism
  • Most likely cause –> Hashimoto’s Disease
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9
Q

What is Hashimoto’s Thyroiditis? Treatment?

A

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

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10
Q

Clinical Case 2 Continued (Hashimoto’s)

A
  • T4 increase is a result of medication; shows patient is compliant
  • TSH in normal range; adequately treated
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11
Q

Clinical Case 3

  • What is disease?
A
  • 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)
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12
Q

Clinical Case 3 Continued: 2ary Hypothyroidism

A

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
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13
Q

Clinical Case 3 Continued: 2ary hypothyroidism

A
  • 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
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14
Q

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?

A

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
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15
Q

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

A
  • 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
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16
Q

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

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

A
  • 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)
17
Q

Clinical Case 5

  • What is the next most important test to determine underlying cause?
A
  • High calcium tends to lead to renal stones
  • Underlying cause likely to be:
    • Malignancy
    • Primary hyperparathyroidism
  • PTH measurement is most useful
18
Q

Clinical Case 5 Continued: renal stones

What is the most likely diagnosis cause?

A

Primary hyperparathyroidism

19
Q

Clinical Case 6

A
  • 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
20
Q
A