Symptomatic hypocalcemia in a patient with latent hypoparathyroidism and breast carcinoma with bone metastasis following administration of pamidronate

Pamidronate is an effective drug used not only in patients with tumor-associated hypercalcemia, but also in normocalcemic patients with metastatic bone disease to relieve pains. We describe a 39-year-old normocalcemic patient with subclinical hypoparathyroidism and bone metastasis due to breast carcinoma. Following parenteral administration of 60 mg pamidronate, the corrected serum level of calcium decreased from 2.12 mmol/l (=8.9 mg/dl) to 1.42 mmol/l (5.7 mg/dl), accompanied with carpal pedal spasm. The present case indicates that the hypocalcemia due to latent hypoparathyroidism was compensated by extensive osteolysis due to bone metastasis, and that overt hypocalcemia may develop after intravenous administration of pamidronate in such a patient.