Two days after parathyroidectomy for severe primary hyperparathyroidism with osteitis fibrosa cystica, a patient develops tetany. Calcium is 5.8 mg/dL, phosphate is 1.6 mg/dL (low), alkaline phosphatase is markedly elevated, and intact PTH is 60 pg/mL. The most likely explanation is:

• A Permanent hypoparathyroidism from accidental removal of all glands
• B Hungry bone syndrome due to rapid mineralisation of depleted bone ✓
• C Hypomagnesaemia-induced functional hypoparathyroidism
• D Recurrent laryngeal nerve injury causing hyperventilation alkalosis

Explanation

Hungry bone syndrome occurs after correction of longstanding severe hyperparathyroidism, especially with preoperative alkaline phosphatase elevation and radiological bone disease. Rapid calcium and phosphate deposition into remineralising skeleton causes profound hypocalcaemia with hypophosphataemia and a PTH that is detectable or even high, matching this picture. Permanent hypoparathyroidism gives a low PTH with high phosphate, so option A is excluded by both the PTH value and the low phosphate.

Reference: Williams Textbook of Endocrinology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.