Hypercalcemia of Malignancy Attributed to Cosecretion of PTH and PTHRP in Lung Adenocarcinoma

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, while less than 1% of all cases are due to ectopic secretion of parathyroid hormone. Case report: We present an unusual case of HCM due to proposed cosecretion 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 was improved with administration of denosumab. Conclusion: This is the youngest and first case of hypercalcemia of malignancy attributed to cosecretion of PTH and PTHrP from an adenocarcinoma. In refractory cases of HCM, denosumab is a potential option when other conventional measures are unsuccessful. ; https://doi.org/10.1016/j.aace.2021.01.003