Tricky Biochemistry Multiple Choice Questions And Answers

36- An Afro-Carribean male aged 48 years presents with gradual onset of exertional dyspnoea, non productive cough, malaise, weight loss and polyarthralgia. Schirmers test indicates a dry eye. X-ray of the hand shows punched out osteopenic lesions. Which of the following investigation is unlikely to be helpful in establishing the diagnosis of this condition:
1) Serum calcium
2) Serum phosphorus
3) Urea and electrolytes
4) Thallium Scan
5) Quantitative Immunoglobulins.
Answers-4
This condition is sarcoidosis. Serum calcium, Serum phosphorus, Chem7 and Chem 20 and Quantitative Immunoglobulins are all used in establishing the diagnosis.
Gallium scan is helpful in sarcoidosis. (Radiology of extrathoracic sarcoid ...)
Gallium scan vs. Thallium scan.
Gallium scan (radioactive 67Ga) is used to detect inflammation - such as in inflammatory disorders or malignancy.
Thallium (radioactive 201Tl) is a potassium analogue and is used to demonstrate areas of poor perfusion. It is particularly used in cardiology to detect areas of
ischaemia.

37- Polymyalgia rheumatica associated with
1) raised creatinine kinase
2) increased alkaline phosphotase
3) sudden loss of vision in one eye
4) shoulder and pelvic girdle pain in 40 year old man
5) erythema nodosum
Answers-2
Liver enzymes elevated in most patients. Visual disturbances suggestive of temporal arteritis, due to ischaemic changes in ciliary arteries (optic neuritis/infarction) and less commonly due to central artery occlusion. Raised CK in polymyositis. PMR is rare before the age of 50 years.

38- A 73 year old male presented with an acute attack of gout in his left knee. What is the most likely underlying metabolic cause?
1) decreased renal excretion of uric acid
2) endogenous overproduction of uric acid
3) excessive dietary purine intake
4) lactic acidosis
5) starvation
Answers-1
The aetiology of gout can broadly be divided into cases where there is underexcretion of urate via the kidney (90%) or endogenous overproduction of uric acid (10%) although in practical terms the distinction is rarely made as it allopurinol is the mainstay of long-term treatment (not during the acute attack!) in both groups. In a 73 year old man it is almost certainly reduced renal excretion due to deteriorating renal function and possibly diuretic use. Excessive dietary intake of purines is unlikely to be the main cause in this case.

39- Primary hyperparathyroidism may occur in association with the following conditions
1) Chronic renal failure
2) Vitamin D deficiency
3) Gastrinoma
4) Autoimmune polyendocrine syndrome
5) Sjogren's syndrome
Answers-3
The association of primary hyperparathyroidism and a gastrinoma would suggest a diagnosis of multiple endocrine neoplasia type 1. CRF causes secondary or tertiary
hyperparathyroidism, with vit D deficiency causing secondary hyperparathyroidism.
Ther is no association with Sjogren's.

40- With which of the following is hyperprolactinaemia associated?
1) Cabergoline therapy
2) Depression
3) Fluoxetine therapy
4) Hyperthyroidism
5) Sheehan's syndrome
Answers-3
Hyperprolactinaemia may be manifest by a milky discharge from the breasts. Causes include, prolactinoma, hypothyroidism (far increased TRH), Non-functional
tumour with stalk compression and drugs in particular dopamine antagonists such as chlorpromazine, haloperidol and domperidone. Pregnancy is a particularly
common cause of hyperprolactinaemia. Other drugs that are occasionally reported include SSRIs. PCOs is often associated with idiopathic hyperprolactinaemia.

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