Hypercalcemia in dogs with adenocarcinoma derived from apocrine glands of the anal sac. Biochemical and histomorphometric investigations.

Hypercalcemia, hypercalciuria, and hyperphosphaturia were present in female dogs with adenocarcinomas derived from apocrine glands of the anal sac (CA). Remission of hypercalcemia accompanied tumor excision in all six dogs undergoing surgery, whereas tumor recurrence or growth of metastases was associated with a return of hypercalcemia. Preoperatively, the plasma concentrations of immunoreactive parathyroid hormone in all dogs were undetectable or in the low normal range. Plasma concentrations of 13,14-dihydro-15-keto-prostaglandin E2 (PGE2M) and serum 1,25-dihydroxyvitamin D were not significantly different from control dogs. Urinary cyclic AMP and hydroxyproline were increased in dogs with CA. No immunoreactive parathyroid hormone was detected in extracts from tumor tissue, and parathyroid glands from dogs with CA had ultrastructural characteristics of secretory inactivity. Lumbar vertebrae from hypercalcemic dogs had decreased trabecular bone volume and increased osteoclastic bone resorption compared with age-matched control dogs. After tumor excision, serum total calcium returned to the normal range, whereas immunoreactive parathyroid hormone increased 2- to 20-fold and 1,25-dihydroxyvitamin D decreased 2- to 8-fold. Postoperative hypocalcemia was not observed. These results indicate that CA produces a hypercalcemic factor other than immunoreactive parathyroid hormone or prostaglandin E2 that increases osteoclastic osteolysis distant from the tumor and results in hypercalcemia, hypercalciuria, and hyperphosphaturia.