Refractory hypercalcemia caused by parathyroid-hormone-related peptide secretion from a metastatic pancreatic neuroendocrine tumor: a case report

Background: The parathyroid-hormone-related peptide has been shown in earlier studies to be secreted by pancreatic neuroendocrine tumors, although its secretion by gastroenteropancreatic neuroendocrine tumors is very rare. In contrast, a number of solid tumors, such as lung cancer and renal cell carcinoma, have frequently been shown to secrete parathyroid-hormone-related peptide. Case presentation: We describe a case report of a 53-year-old Canadian white patient with refractory parathyroid-hormone-related-peptide-mediated hypercalcemia associated with metastatic pancreatic neuroendocrine tumors and review the available research. Our patient had severe hypercalcemia initially refractory to treatment. Computed tomography scan of the abdomen revealed a pancreatic lesion and multiple hepatic metastases. A liver biopsy confirmed metastatic pancreatic neuroendocrine tumor expressing parathyroid-hormone-related peptide. Circulating parathyroid-hormone-related peptide levels were at the upper limit of normal preoperatively and decreased sharply postoperatively following debulking of the tumor. Blood calcium levels eventually normalized on long-term administration of the somatostatin analog lanreotide in combination with denosumab. Conclusions: We describe a case with parathyroid-hormone-related-peptide-mediated hypercalcemia in a pancreatic neuroendocrine tumor (parathyroid-hormone-related peptide tumor). Refractory hypercalcemia was likely the result of parathyroid-hormone-related peptide overproduction by the tumor and resolved following normalization of parathyroid-hormone-related peptide levels.