Secondary hypoparathyroidism attributed to hypomagnesemia in a dog with protein-losing enteropathy.

Severe hypomagnesemia (0.8 mg/dl; reference range, 1.6 to 2.3 mg/dl), hypocalcemia, and protein-losing enteropathy were identified in a 5-year-old castrated male 3-kg (6.6 lb) Shih Tzu examined because of anorexia, lethargy, paresis, and abdominal distention. Histologic examination of intestinal biopsy specimens revealed lymphangiectasia and lymphocytic, plasmacytic, neutrophilic infiltrates. Initial treatment included administration of magnesium (0.80 mEq/kg [0.36 mEq/lb]) of body weight in a balanced electrolyte solution. This treatment resulted in normalization of the serum magnesium concentration (1.7 mg/dl); resolution of the lethargy, paresis, and tachycardia; and an increase in the serum parathyroid hormone and ionized calcium concentrations. Findings were consistent with secondary hypoparathyroidism attributable to hypomagnesemia. Magnesium concentration should be monitored in all dogs with gastrointestinal tract disease, especially those with protein-losing enteropathy, anorexia, and weakness.