Diagnosing the etiology of hypercalcemia in a dog: a case of primary hyperparathyroidism.

A 13-year-old spayed Labrador Retriever cross dog presented for polyuria and polydipsia. Serum total calcium, free calcium, and intact parathyroid hormone concentrations were elevated. Surgical exploration of the ventral neck revealed a grossly enlarged right external parathyroid gland. The histopathological diagnosis for the excised right parathyroid gland was an incompletely resected parathyroid carcinoma. Parathyroid carcinoma in the dog is an infrequent cause of hypercalcemia and primary hyperparathyroidism.