Hypercalcemia and status epilepticus relates to salmon calcitonin administration in breast cancer

Calcitonin is currently used to treat hypercalcemia of many clinical types. However, we encountered a woman who suffered severe hypercalcemia and status epilepticus, both of which developed 8 days after the administration of salmon calcitonin for the treatment of breast cancer. When the patient first presented her serum calcium level was 15.5 mg/dl, intact parathyroid hormone level 118 pg/ml, calcitonin <2 pg/ml, magnesium 1.2 mg/dl, and phosphate 1 mg/dl. Her serum calcium level returned to the reference range within 48 h after correction. At follow-up no hypercalcemia had developed, although the patient had received no further treatment for her breast cancer and multiple metastases were subsequently detected. Her hypercalcemia is ascribed to exogenous calcitonin supplementation. These conflicting events may be due to functionally heterogeneous calcitonin receptors or to activation of 1α-hydroxylase by exogenous calcitonin.