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C. Ward1
1University of Georgia College of Veterinary Medicine, Small Animal Medicine and Surgery, Athens, USA
Cynthia R. Ward, VMD, PhD, DACVIM
University of Georgia College of Veterinary Medicine Athens, GA USA
Small animal patients presenting with a primary complaint of hypercalcemia can often be a diagnostic challenge. Typically, the clinical signs are insidious and nonspecific. A thorough work-up, sometimes necessitating repetition in diagnostic steps may be required to determine the etiology of the hypercalcemia. Treatment should be directed toward resolution of the underlying disease.
Serum ionized calcium is regulated within a narrow range that is controlled by two principal hormones: parathyroid hormone (PTH) and the active form of
vitamin D, calcitriol. PTH, synthesized by the chief cells
of the parathyroid gland, acts on the bone to increase resorption and calcium mobilization. It also works on the kidney to increase calcium reabsorption and decrease phosphorous reabsorption, and to increase the formation of calcitriol. The net result of PTH secretion is to increase calcium and decrease phosphorous in the serum. Vitamin D is formed from cholesterol precursors in the skin by the action of sunlight. The active form, calcitriol, is formed in the kidney. Vitamin D works primarily on
the intestine to increase calcium and phosphorous absorption. The net effect of vitamin D is to increase plasma calcium and phosphorous.
Causes of hypercalcemia
The most common cause of hypercalcemia in dogs and cats is malignancy. The neoplastic diseases reported
to cause hypercalcemia include lymphoma, anal sac apocrine cell adenocarcinoma, multiple myeloma, mammary carcinoma, thymoma, oral melanoma hepatoblastoma, chronic lymphocytic leukemia, and nasal carcinoma, with lymphoma being the most common. Hypercalcemia seen with malignant disease probably results primarily from enhanced osteoclastic bone resorption mediated by factors systemically released by neoplastic cells. One such factor has been has been identified in the dog as parathyroid hormone related protein (PTHrP) which is identical to PTH at the N-terminal region and can bind with equal affinity to PTH receptors. By activating PTH receptors, PTHrP causes
25-28 September, 2018 | Singapore
Vet Clinics of North America Small Animal Practice Palliative Medicine and Hospice Care, 2011
Lascelles BD, Management of Chronic Cancer Pain, Withrow and MacEwen’s Small Animal Clinical Oncology 5th edition pp 245-259
Wakshlag JJ, Nutritional Management of the Cancer Patient Withrow and MacEwen’s Small Animal Clinical Oncology 5th edition pp 259-270
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