Hypercalcemia of Malignancy Attributed to Co-Secretion of PTH and PTHrP in Lung Adenocarcinoma

ABSTRACT Introduction Hypercalcemia of malignancy (HCM) portends a very poor prognosis and no established guidelines exist regarding its management. Most instances of HCM are due to local osteolysis or secretion of parathyroid hormone related-peptide (PTHrP) while less than 1% of all cases of are due to ectopic secretion of parathyroid hormone (PTH). Case Report We present an unusual case of HCM due to proposed co-secretion of both parathyroid hormone and parathyroid hormone-related protein in a 36-year-old man with a poorly-differentiated lung adenocarcinoma. The patient’s hypercalcemia was refractory to conventional measures including intravenous bisphosphonate therapy (zoledronic acid) and improved with administration of denosumab. Conclusion This patient represents the youngest known example, and the first from an adenocarcinoma, of this very rare phenomenon. In refractory cases of HCM, denosumab is a potential option when other conventional measures are unsuccessful.