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Primary Hyperparathyroidism — RACP Adult Medicine MCQ

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EasyEndocrinologyPrimary HyperparathyroidismRACP Adult Medicine

A 60-year-old woman presents with fatigue, polyuria, constipation, and confusion. Corrected calcium is 3.5 mmol/L. PTH is 25 pmol/L (very elevated). Phosphate is 0.7 mmol/L (low). 25-OH vitamin D is normal. ALP is elevated. She has bilateral kidney stones. What is the most likely diagnosis?

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Correct answer: D — Primary hyperparathyroidism

Hypercalcaemia + elevated PTH + hypophosphataemia + renal stones = primary hyperparathyroidism. PTH is inappropriately elevated for the calcium level (should be suppressed). Causes: solitary parathyroid adenoma (~85%), hyperplasia (~10-15%), carcinoma (~1%). Surgical indications: symptomatic (stones, bones, groans, moans), calcium >0.25 mmol/L above ULN, eGFR <60, age <50, BMD T-score <-2.5, or vertebral fracture. Preoperative localisation: sestamibi scan + USS.

Reference: Endocrine Society – 2024 – PHPT; ESA 2024