Post-surgery severe hypocalcemia in primary hyperparathyroidism preoperatively treated with zoledronic acid

Zoledronic acid is a newly FDA-approved bisphosphonate for the treatment of hypercalcemia of malignancy. Although the safety and efficacy of this drug in treating hypercalcemia associated with hyperparathyroidism have not yet been established in clinically controlled trials, its off-label use is not uncommon. We describe a patient with primary hyperparathyroidism treated with zoledronic acid who developed severe postoperative hypocalcemia. A 64-yr-old woman was admitted with severe hypercalcemia. She was treated with rehydration, calcitonin, methylprednisolone, furosemide as well as 4 mg/day of zoledronic acid for two consecutive days. Primary hyperparathyroidism caused by a right inferior parathyroid lesion was diagnosed. While awaiting surgery, she continued furosemide, methylprednisolone and hydration: after one week, serum calcium had fallen to such a low level that a short-term calcium carbonate supplementation was required. Three weeks after admission, the patient underwent selective right inferior parathyroidectomy, followed by reduction of PTH. During the postoperative period the patient presented severe hypocalcemia resistant to the usual treatment. Serum calcium levels returned to normal three months after surgery. The severity of hypocalcemia and the resistance to conventional treatments suggest that the effect of hungry bone syndrome could be worse in patients treated with bisphosphonates in the preoperative phase.