Hypercalcemia as a Presenting Clinical Manifestation of Adenocarcinoma of the Colon

Hypercalcemia is rarely associated with colon cancer. It is related to overexpression of parathyroid hormone-related protein (PTH-rp) in malignant cells of the primary colon tumor and metastases. A 44 year old lady presented for evaluation of severe hypercalcemia (15.7 mg/dL) associated with abdominal pain, nausea and constipation. She was diagnosed with metastatic colon cancer involving the liver. Therapy for hypercalcemia consisted of intravenous bisphosphonate and saline hydration. Hypercalcemia remained resistant and refractory to treatment despite resection of the colon tumor. She died soon after admission to hospice. It is proposed that malignant cells of the primary colon tumor and distant metastases, in this patient, were the site of ectopic PTH-rp secretion resulting in hypercalcemia. This case illustrates the significance of recognizing hypercalcemia as a potential clue in detecting underlying colon cancer involving overproduction of PTH-rp. It also exemplifies the poor prognosis expected with this type of humoral hypercalcemia of malignancy and the difficulty encountered when trying to achieve normalization of calcium in this setting.