What is the most common disease that causes hypercalcemia in dogs?

Hypercalcemia, or elevated calcium levels in the blood, can result from several conditions, but lymphosarcoma is recognized as the most common neoplastic cause of this condition in dogs. Lymphosarcoma, or lymphoma, is a cancer of the lymphatic system that can lead to an increase in calcium levels due to the production of parathyroid hormone-related peptide (PTHrP) by the tumor cells. PTHrP mimics the action of parathyroid hormone, promoting the mobilization of calcium from the bones and increasing renal tubular reabsorption of calcium, thereby raising serum calcium concentrations.

While chronic kidney disease can also lead to hypercalcemia in some cases, it typically causes the opposite effect, leading to hypocalcemia or normal calcium levels because the kidneys are less able to handle calcium excretion. Similarly, hypoadrenocorticism (Addison's disease) more commonly presents with hypocalcemia, not hypercalcemia. Lastly, hypoparathyroidism results in low calcium levels due to insufficient production of parathyroid hormone, which serves to increase calcium levels.

Thus, lymphosarcoma stands out as the primary condition associated with hypercalcemia in dogs, making it the correct answer in