Severe prolonged hypocalcaemia following pamidronate for malignant hypercalcaemia

Hypercalcaemia of malignancy is a frequent occurrence. First line treatment of this condition involves the use of bisphosphonates. This report sets out the clinical findings in a patient presenting with metastatic breast cancer and hypercalcaemia (corrected serum calcium 3.72 mmol/l) who had received previous surgery for a parathyroid adenoma. After treatment with pamidronate, profound, prolonged (more than 60 days) symptomatic hypocalcaemia was observed. We discuss the possible explanations for these observations and conclude that a normal parathyroid reserve is probably necessary for the smooth normalization of blood calcium when bisphosphonates are used to treat malignant hypercalcaemia.