Two days after parathyroidectomy for severe primary hyperparathyroidism, a patient develops tetany. Calcium is 6.0 mg/dL, phosphate is 2.0 mg/dL (low), magnesium is normal, and intact PTH is undetectable. Urinary calcium excretion is very high. The mechanism responsible is:

• A Permanent hypoparathyroidism from inadvertent gland removal
• B Magnesium deficiency impairing PTH secretion
• C Renal phosphate retention raising serum phosphate and lowering calcium
• D Rapid remineralisation of chronically starved bone sequestering calcium and phosphate ✓

Explanation

Hungry bone syndrome follows removal of a long-standing, severely hypercalcaemia-driving adenoma. Sudden withdrawal of PTH-driven resorption lets osteoblasts avidly take up calcium, phosphate, and magnesium into bone, producing profound hypocalcaemia with hypophosphataemia and low PTH. Option A is killed by the low phosphate, since surgical hypoparathyroidism causes phosphate retention and hyperphosphataemia. Management is aggressive calcium and vitamin B replacement, sometimes over weeks.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.