AMC MCQ Endocrinology Questions: 10 Free Practice MCQs
Ten AMC MCQ-style endocrinology questions with the answer and the reasoning behind it. They come from the AU.med bank, which has 12 endocrinology questions and many more across every topic.
1 / 10
A 65-year-old male heavy smoker presents with confusion, lethargy, and constipation. Serum calcium is 3.2 mmol/L (reference 2.15-2.55) and PTH is suppressed (<0.5 pmol/L). Chest X-ray reveals a hilar mass.
What is the mediator of this hypercalcaemia?
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Answer: A. PTH-related Peptide (PTHrP)
Why: Humoral Hypercalcaemia of Malignancy (HHM) is most commonly caused by secretion of Parathyroid Hormone-related Peptide (PTHrP) by squamous cell carcinomas (e.g., lung, head and neck). PTHrP activates PTH-1 receptors in bone and kidney, elevating calcium while endogenously suppressing native PTH.
- B. Incorrect. Primary hyperparathyroidism presents with elevated or inappropriately normal serum PTH, unlike malignant PTHrP secretion.
- C. Incorrect. Calcitriol (1,25-OH2 Vit D) excess hypercalcaemia is characteristic of granulomatous diseases (sarcoidosis) or lymphomas.
- D. Incorrect. Osteolytic bone metastases cause local osteolysis, but systemic PTHrP release is the classic mediator of humoral hypercalcaemia with a hilar mass.
Sources: Endocrinology Guidelines
2 / 10
A 28-year-old woman with a history of Graves' disease is admitted with severe agitation, hyperpyrexia (39.8°C), tachycardia (148 bpm, atrial fibrillation), and mild jaundice. She recently had an emergency appendectomy.
Which of the following is the most likely diagnosis?
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Answer: B. Thyroid storm (thyrotoxic crisis)
Why: Thyroid storm is an endocrine emergency triggered by stress (surgery, infection, trauma) in patients with uncontrolled hyperthyroidism. The Burch-Wartofsky Point Scale is used for clinical diagnosis, assessing thermoregulatory dysfunction, cardiovascular effects (tachycardia, AF, heart failure), GI-hepatic dysfunction (jaundice), and CNS agitation. Treatment involves a multi-drug regimen to block hormone synthesis, release, and peripheral conversion.
- A. While sepsis can cause fever and tachycardia, the history of Graves' disease, atrial fibrillation, and jaundice suggests a severe hyperthyroid crisis.
- C. Pheochromocytoma crisis presents with severe hypertension, headache, and sweating; hyperpyrexia to 40°C and jaundice are less typical.
- D. Malignant hyperthermia occurs during anesthesia exposure to inhalational agents or succinylcholine, not as a subacute postoperative presentation.
Sources: eTG complete — Endocrine — Thyroid Storm; Endocrine Society Clinical Practice Guidelines on Hyperthyroidism
3 / 10
A 35-year-old woman presents to her GP with episodes of sudden-onset pounding headaches, profuse sweating, and palpitations. On examination in the clinic, her blood pressure is 185/110 mmHg, and her heart rate is 108 bpm. She has no significant past medical history.
Which of the following is the most appropriate initial screening test to confirm a diagnosis of phaeochromocytoma?
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Answer: A. 24-hour urinary fractionated metanephrines or plasma free metanephrines
Why: Phaeochromocytoma is a rare catecholamine-secreting tumor of the adrenal medulla. The diagnosis must always be established biochemically before imaging is performed. High-sensitivity screening tests include 24-hour urinary fractionated metanephrines or plasma free metanephrines. If these are elevated, an abdominal CT or MRI is then performed to localize the tumor.
- B. Biochemical confirmation must precede any localization imaging to avoid finding incidentalomas and to guide patient safety protocols.
- C. ARR is the screening test for primary aldosteronism (Conn's), not for catecholamine-producing phaeochromocytomas.
- D. The metyrapone test is used in the workup of ACTH-dependent Cushing's syndrome, not phaeochromocytoma.
Sources: eTG complete — Endocrine — Adrenal Disorders; Endocrine Society Clinical Practice Guidelines on Pheochromocytoma
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4 / 10
A 22-year-old man with type 1 diabetes is being treated for severe diabetic ketoacidosis (DKA) with intravenous fluids and a fixed-rate insulin infusion. His blood glucose has dropped from an initial 28 mmol/L to 13.5 mmol/L, but his serum ketones remain elevated at 3.2 mmol/L and venous pH is 7.21.
Which of the following is the most appropriate management adjustment according to the Therapeutic Guidelines (eTG)?
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Answer: B. Introduce intravenous 5% Dextrose alongside the sodium chloride solution, and continue the insulin infusion at the same rate
Why: In the management of DKA, the goal of the insulin infusion is to suppress lipolysis and clear ketosis, not just to normalize blood glucose. When blood glucose falls below 14 mmol/L, IV 5% or 10% dextrose must be commenced alongside saline. This prevents hypoglycemia and allows the insulin infusion to be maintained at a rate sufficient to clear ketones (ketones < 0.6 mmol/L and pH > 7.30).
- A. Stopping insulin while ketones are elevated will cause a rapid recurrence of ketoacidosis and is highly dangerous.
- C. The patient remains in DKA (pH 7.21, ketones 3.2). Fixed-rate IV insulin must be maintained until ketosis is fully cleared.
- D. Bicarbonate is not indicated in DKA unless the pH is extremely low (< 6.9) due to risks of paradoxically worsening intracellular acidosis.
Sources: eTG complete — Endocrine — Diabetic Ketoacidosis; ADS (Australian Diabetes Society) DKA Guidelines
5 / 10
A 68-year-old man is brought to the Emergency Department with profound weakness. His blood tests reveal a serum potassium of 6.9 mmol/L and an ECG showing peaked T waves and PR prolongation.
Which of the following represents the most appropriate immediate sequence of interventions?
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Answer: C. Intravenous Calcium gluconate (or Calcium chloride), followed by intravenous insulin-dextrose infusion and inhaled Salbutamol
Why: Severe hyperkalemia (> 6.5 mmol/L or with ECG changes) is a cardiac emergency. The first step is to administer IV calcium (gluconate or chloride) to stabilize the cardiac membrane and reduce arrhythmia risk. Next, short-term intracellular potassium shifts are achieved using IV insulin-dextrose (shifts K+ via Na+/K+ ATPase activation) and nebulised Salbutamol (beta-2 agonist effect). Finally, potassium elimination is achieved using loop diuretics, oral binders (SZC), or hemodialysis.
- A. Oral binders and dialysis are slow or complex; they do not provide the immediate cardiac protection required for active ECG changes.
- B. Spironolactone is a potassium-sparing diuretic and is strictly contraindicated in hyperkalemia as it would worsen the condition.
- D. Furosemide promotes urinary excretion but acts too slowly to protect the heart in the presence of acute cardiotoxic ECG changes.
Sources: eTG complete — Cardiovascular — Hyperkalaemia; AMH — Endocrine Guidelines
6 / 10
An 82-year-old woman with a history of ischemic heart disease is diagnosed with primary hypothyroidism. Her TSH is 18 mIU/L and free T4 is low.
What is the most appropriate starting dose of Levothyroxine for this patient?
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Answer: A. 12.5 to 25 mcg daily, with slow titration every 6–8 weeks
Why: In elderly patients and those with known coronary artery disease, thyroxine replacement must be initiated at a very low dose (typically 12.5–25 mcg daily) and titrated slowly (increases of 12.5–25 mcg every 6–8 weeks) based on clinical response and TSH levels. Rapid replacement can increase cardiac demand and precipitate angina, myocardial infarction, or arrhythmias.
- B. A full replacement dose can precipitate myocardial ischemia, angina, or tachyarrhythmia in elderly patients with pre-existing heart disease.
- C. TSH takes 6-8 weeks to stabilize, and 50 mcg is too high a starting dose for a patient with cardiac disease.
- D. Weekly dosing is not standard practice for initiating thyroid hormone replacement.
Sources: Australian Medicines Handbook (AMH); eTG complete — Endocrine
7 / 10
A 65-year-old man with metastatic lung cancer presents with progressive confusion, constipation, and polyuria. His corrected serum calcium is 3.45 mmol/L. His ECG is normal.
What is the most appropriate initial step in the management of this patient's hypercalcemia?
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Answer: B. Intravenous fluid resuscitation with 0.9% Sodium Chloride
Why: Severe hypercalcemia (calcium > 3.5 mmol/L or symptomatic > 3.0 mmol/L) causes nephrogenic diabetes insipidus and vomiting, leading to profound dehydration. The first and most critical management step is volume expansion with intravenous 0.9% sodium chloride (typically 3–6 liters in 24 hours) to restore GFR and increase urinary calcium excretion. Bisphosphonates (like zoledronic acid) are given after hydration is initiated.
- A. Bisphosphonates take 2-4 days to exert their maximal calcium-lowering effect and are not the first step prior to hydration.
- C. Calcium carbonate is a calcium supplement and would worsen severe hypercalcemia.
- D. Hemodialysis is reserved for refractory hypercalcemia in the setting of severe renal failure or heart failure where hydration is impossible.
Sources: eTG complete — Endocrine — Hypercalcaemia; AMH
8 / 10
A 42-year-old woman is found to have a solitary 1.5 cm nodule in the right lobe of her thyroid during a carotid ultrasound. She has no compressive symptoms, dysphagia, or family history of thyroid cancer. Her serum TSH is 1.2 mIU/L (normal 0.4–4.0).
What is the most appropriate next step in the clinical evaluation of this thyroid nodule?
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Answer: B. Refer for an ultrasound-guided Fine-Needle Aspiration (FNA) biopsy of the nodule
Why: In patients with a thyroid nodule > 1 cm, the initial step is to check the TSH level. If TSH is normal or high, a diagnostic thyroid ultrasound should be performed to assess features (calcifications, hypoechogenicity, margins). Ultrasound-guided Fine-Needle Aspiration (FNA) is indicated based on size and sonographic risk classification (such as the ACR TI-RADS criteria) to exclude malignancy.
- A. Radioactive scans are used to evaluate hyperfunctioning ('hot') nodules in the setting of a suppressed (low) TSH, not a normal TSH.
- C. A 1.5 cm nodule is large enough to warrant formal risk stratification and potential biopsy, rather than simple delayed observation.
- D. Surgery is not indicated before establishing cytological diagnosis via FNA, unless there are signs of severe airway compression.
Sources: Endocrine Society of Australia (ESA) Thyroid Nodule Guidelines; ATA (American Thyroid Association) Guidelines on Thyroid Nodules
9 / 10
A 19-year-old male with type 1 diabetes is admitted with diabetic ketoacidosis (DKA). His blood glucose is 24 mmol/L, blood ketones are 4.8 mmol/L, and pH is 7.15. His serum potassium is reported as 3.0 mmol/L.
Which of the following is the most appropriate initial management step regarding insulin and electrolyte replacement?
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Answer: B. Administer aggressive fluid resuscitation and potassium replacement, withholding insulin until the serum potassium is > 3.3 mmol/L
Why: In the management of diabetic ketoacidosis (DKA), serum potassium must be checked before starting insulin. If potassium is < 3.3 mmol/L, insulin infusion must be delayed, and potassium should be aggressively replaced (usually via central line or large peripheral bore) until it rises above 3.3 mmol/L. This prevents severe, life-threatening hypokalemia driven by insulin-mediated intracellular shifts.
- A. Starting insulin when potassium is < 3.3 mmol/L is contraindicated, as insulin shifts potassium intracellularly and can cause fatal arrhythmias.
- C. Bolus insulin is not recommended in DKA management guidelines, and administering it with low potassium is dangerous.
- D. Bicarbonate therapy is not routinely recommended in DKA unless the pH is < 6.9, and it would further lower serum potassium.
Sources: ADEA/ADS DKA Guidelines; eTG complete — Endocrine
10 / 10
A 45-year-old man presents with difficult-to-control hypertension (165/100 mmHg on Amlodipine and Perindopril). Routine biochemistry reveals: Sodium 144 mmol/L, Potassium 3.1 mmol/L (low). A morning blood sample shows a suppressed plasma renin activity and elevated plasma aldosterone concentration.
What is the most likely diagnosis?
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Answer: C. Primary hyperaldosteronism (Conn's syndrome)
Why: Primary hyperaldosteronism (Conn's syndrome) is characterized by autonomous aldosterone production by the adrenal cortex, leading to sodium retention, potassium wasting, and suppressed renin levels. Screening is performed using the aldosterone-to-renin ratio (ARR) in patients with resistant hypertension or hypertension with hypokalemia.
- A. Renal artery stenosis causes secondary hyperaldosteronism, which would present with elevated renin, not suppressed renin.
- B. Cushing's syndrome causes hypertension but is driven by cortisol excess and typically presents with physical signs like striae and buffalo hump.
- D. The patient is not taking a diuretic (he is on an ARB/ACEi and CCB), making this drug effect impossible.
Sources: eTG complete — Endocrine — Adrenal Disorders; Endocrine Society of Australia Clinical Practice Guidelines on Primary Aldosteronism
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Exam-style questions written by MedHub for practice. They are not official exam questions.