Bisphosphonate-induced hypocalcemia associated with vitamin D deficiency in a patient with advanced cancer.

A case is presented of symptomatic hypocalcemia following treatment with bisphosphonates. This patient also had deficiency of 25 hydroxyvitamin D that was unrecognized. The use of bisphosphonates in cancer is increasing, not only in the treatment of hypercalcemia, but also for bone pain and to decrease the risk of skeletal morbidity in metastatic breast cancer, multiple myeloma, and Paget's disease in normocalcemic patients. The patient was probably vitamin D deficient because of a combination of poor oral intake, inadequate sunlight exposure, and the development of renal failure. However despite receiving both parenteral and oral calcium therapy, the serum calcium remained low until the replacement of vitamin D. With increasing use of bisphosphonate therapy in malignant disease, we believe that an assessment of vitamin D status, calcium intake, renal function, phosphate, magnesium, and albumin should be undertaken prior to initiating therapy in most palliative care patients.