Hypocalcemia and an inappropriate endocrine response in osteoblastic metastatic breast cancer

Hypercalcemia in association with skeletal metastases is common; hypocalcemia in this clinical setting is unexpected, though it has also been described, most commonly with primary lesions of the breast or prostate. In a subset of hypocalcemic patients with breast cancer, there is an inappropriate endocrinologic response as evidenced by a relative hypoparathyroidism and an elevation in the serum level of calcitonin. We have described a representative case and reviewed the literature.