A 34-year-old woman undergoes successful parathyroidectomy for primary hyperparathyroidism with a preoperative calcium of 13.5 mg/dL. On postoperative day 2 she develops carpopedal spasm with calcium 6.0 mg/dL, phosphate 1.8 mg/dL (low), and alkaline phosphatase 420 U/L. Intravenous calcium infusion produces only transient correction. What is the diagnosis?
- A Hypomagnesaemia causing functional hypoparathyroidism
- B Permanent hypoparathyroidism from inadvertent gland removal
- C Hungry bone syndrome ✓
- D Osteoporosis-related pathological hypocalcaemia
Correct answer: C. Hungry bone syndrome
Explanation
Hungry bone syndrome occurs after removal of a long-standing high-turnover parathyroid lesion, typically when alkaline phosphatase is markedly elevated. Sudden withdrawal of PTH-driven osteoclast activity causes massive skeletal uptake of calcium, phosphate and magnesium, producing profound hypocalcaemia that is difficult to correct. The combination of low calcium with LOW phosphate and high alkaline phosphatase distinguishes it from surgical hypoparathyroidism, where phosphate is characteristically high due to reduced renal excretion.
Reference: Williams Textbook of Endocrinology, 14th ed.
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