Anal sac apocrine gland adenocarcinoma in dogs is commonly associated with which electrolyte abnormality?

• A. Hypercalcemia
• B. Hypocalcemia
• C. Hyperkalemia
• D. Hypophosphatemia

Answer: (A)

Anal sac adenocarcinoma commonly causes hypercalcemia through a paraneoplastic effect. Many tumors secrete PTH-related peptide (PTHrP), which mimics parathyroid hormone. PTHrP raises blood calcium by stimulating bone resorption and increasing renal calcium reabsorption, leading to a humoral hypercalcemia of malignancy. This elevated calcium can produce symptoms such as increased thirst and urination, vomiting, anorexia, and weakness. Phosphate is often affected as well (often low) due to PTHrP activity, but the hallmark abnormality is high calcium.