A 42-year-old man undergoes parathyroidectomy for severe primary hyperparathyroidism; preoperative alkaline phosphatase was 980 U/L with radiological osteitis fibrosa cystica. Twelve hours after successful excision of a 3 g adenoma, serum calcium is 6.1 mg/dL with phosphorus 1.8 mg/dL (low) and magnesium 1.4 mg/dL. He is tetanic and PTH is undetectable. The most likely explanation is:

• A Postoperative hypomagnesaemia alone causing functional hypoparathyroidism
• B Inadvertent removal of all four parathyroid glands
• C Hungry bone syndrome due to rapid mineralisation of depleted bone ✓
• D Citrate toxicity from intraoperative fluid administration

Explanation

Hungry bone syndrome follows correction of long-standing, high-turnover hyperparathyroidism, predicted by very high preoperative alkaline phosphatase and radiographic bone disease. Rapid skeletal uptake of calcium and phosphate produces profound hypocalcaemia with HYPOphosphataemia. Surgical hypoparathyroidism, the chief distractor, gives hypocalcaemia with HYPERphosphataemia from loss of the phosphaturic action of PTH. Management is aggressive intravenous calcium, often with magnesium replacement and calcitriol, sometimes needing prolonged infusion.

Reference: Williams Textbook of Endocrinology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.