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Sarcoid Hypercalcaemia — RACP Adult Medicine MCQ

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ModerateEndocrinologySarcoid HypercalcaemiaRACP Adult Medicine

A 50-year-old man with sarcoidosis presents with mild hypercalcaemia (corrected calcium 2.85 mmol/L). PTH is suppressed. 1,25-dihydroxyvitamin D is elevated (250 pmol/L). 25-OH vitamin D is normal. ACE is elevated. He has bilateral hilar lymphadenopathy and skin lesions. What is the mechanism of hypercalcaemia?

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Correct answer: B — Sarcoidosis

Hypercalcaemia with suppressed PTH and elevated 1,25(OH)₂D in sarcoidosis is due to extrarenal 1-alpha-hydroxylase activity in granuloma macrophages. The macrophages convert 25-OH-D to 1,25(OH)₂D autonomously (bypassing normal PTH-regulated renal conversion). Treatment: corticosteroids (suppress granulomatous inflammation and 1-alpha-hydroxylase activity), avoid calcium/vitamin D supplements, avoid sun exposure. Same mechanism in other granulomatous diseases (TB, lymphoma, berylliosis).

Reference: BTS – 2020 – Sarcoidosis; eTG Endocrine 2024