Hypercalcaemia in a dog with lymphoma without increases in parathyroid hormone, parathyroid hormone-related protein and vitamin D metabolites concentrations

Lymphoma is one of the most common causes of hypercalcaemia in dogs. Typically, the hypercalcaemic state is driven by ectopic production of parathyroid hormone-related protein by the malignant lymphoma cells. In this case report, the authors describe the diagnosis of lymphoma in a dog with hypercalcaemia which had a plasma parathyroid hormone-related protein concentration within the reference range. Furthermore, circulating concentrations of the two other main hormones which are known to increase serum calcium concentrations, namely parathyroid hormone and 1,25 dihydroxyvitamin D, were also below the upper limits of their respective reference ranges. This case report highlights that hypercalcaemia is not invariably mediated by increases in circulating concentrations of parathyroid hormone-related protein. In addition, it emphasises the need to further investigate the pathophysiology of malignancy-related hypercalcaemia in dogs.