Primary Hyperparathyroidism — SCE Rheumatology MCQ

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ModerateMetabolic Bone DiseasePrimary HyperparathyroidismSCE Rheumatology

A 55-year-old man presents with bone pain and proximal muscle weakness. His albumin-adjusted serum calcium is 2.65 mmol/L on two separate measurements (reference range 2.20–2.60), phosphate is 0.62 mmol/L (0.80–1.50), alkaline phosphatase is 220 U/L (30–130), and parathyroid hormone is 8.5 pmol/L (1.6–6.9). His 25-hydroxyvitamin D concentration and renal function are normal. What is the most likely diagnosis?

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Correct answer: A — Primary hyperparathyroidism

The correct answer is primary hyperparathyroidism. Repeated hypercalcaemia with a concurrently elevated PTH indicates PTH-dependent hypercalcaemia; the low phosphate reflects PTH-mediated renal phosphate wasting. The raised alkaline phosphatase is compatible with increased skeletal turnover in symptomatic disease but is not independently diagnostic. Sarcoidosis and myeloma can cause hypercalcaemia, but endogenous PTH should be suppressed. Vitamin D deficiency usually produces secondary hyperparathyroidism with low or normal calcium, and the vitamin D concentration is normal here. Paget disease may cause bone pain and raised alkaline phosphatase, but calcium, phosphate and PTH are generally normal. Urinary calcium excretion should subsequently be measured to exclude familial hypocalciuric hypercalcaemia, as recommended by NICE.

Reference: National Institute for Health and Care Excellence. Hyperparathyroidism (primary): diagnosis, assessment and initial management. NICE guideline NG132, diagnostic testing and Evidence review B, 2019. https://www.nice.org.uk/guidance/ng132/evidence/b-diagnostic-tests-pdf-6782710575