Endocrine Abstracts

Introduction: Hungry bone syndrome (HBS) is a rare complication of parathyroidectomy for primary hyperparathyroidism. We report a case of HBS after parathyroid surgery for severe primary hyperparathyroidism.

Case presentation: A 46-year-old woman was admitted with generalized weakness and difficulty walking due to progressive worsening of low-back pain. Clinical examination revealed tachycardia at 110 bpm and chest deformity. Laboratory results revealed hypercalcemia at 185 mg/l and hypophosphatemia at 19 mg/l. The parathyroid hormone (PTH) concentration was at 4936 pg/ml (normal 15–65) and the alkaline phosphatase concentration reached478 U/l (normal 40–150). Medical treatment was initiated with rehydration, forced diuresis and intravenous infusion of biphosphonates. Ultrasound of the neck and Sestamibi scan showed a localized adenoma. The parathyroidectomy was performed and anatomopathological examination confirmed parathyroid adenoma, weighing 4 g and measuring 3*2*0.6 cm. The postoperative period was characterized by prolonged hypocalcemia, hypophosphatemia and normal PTH levels, which was consistent with the diagnosis of HBS. The patient was discharged on high doses of calcium carbonate and alfacalcidol.

Discussion: HBS refers to the rapid, profound, and prolonged hypocalcaemia associated with hypophosphatemia and hypomagnesaemia, and is exacerbated by suppressed PTH levels, which follows parathyroidectomy in patients with severe primary hyperparathyroidism and preoperative high bone turnover. Although HBS does not have a consensus definition, most resources define it as profound hypocalcemia of less than 8.4 mg/dl that persists for more than four days post-operatively. The severe hypocalcaemia is believed to be due to the greatly increased skeletal usage of calcium, thought to occur as a result of removal of the effect of high circulating parathyroid hormone (PTH) levels on bone, with immediate arrest of bone resorption in the face of continuing and enhanced bone formation. The duration of the HBS is the time taken to remineralise the skeleton, which is also mirrored by normalisation of bone turnover markers, by healing of radiological features of osteitis fibrosa cystica and brown tumours and by significant gains in bone mass. Treatment is aimed at replenishing the severe calcium deficit and at restoring normal bone turnover with the use of high doses of calcium and active metabolites or analogues of vitamin D.

Conclusion: HBS is relatively uncommon, but a serious side effect of parathyroidectomy. It can bring significant morbidity related to the consequences of hypocalcaemia in the case of patients in whom it is not recognized and corrected promptly.