Relationship between serum magnesium, calcium, and parathyroid concentrations in dogs with abnormally low serum 25‐hydroxyvitamin D concentration and chronic or protein‐losing enteropathy

BACKGROUND: The relationship between the development of SHPT and ionized magnesium (iMg) concentrations in blood of dogs with chronic gastrointestinal (GI) disease and abnormally low 25(OH)D is undefined. OBJECTIVES: Evaluate relationships between ionized magnesium (iMg), PTH, ionized calcium (iCa), and 25(OH)D in dogs with chronic enteropathy (CE) with or without protein‐losing enteropathy (PLE) and abnormal 25(OH)D. Determine whether dogs with CE or PLE, decreased 25(OH)D and SHPT have differences in iMg, iCa, or 25(OH)D when compared to dogs that do not have SHPT. ANIMALS: Fifty dogs with CE +/− PLE and abnormally low serum 25(OH)D. METHODS: Retrospective search of submissions database at a veterinary diagnostic laboratory for vitamin D profiles submitted in years 2017 to 2020. Cases were excluded if supplemented with Ca, Mg, or vitamin D. Spearman correlation was performed to evaluate relationships between iMg, PTH, 25(OH)D, and iCa. Ionized Mg, iCa, and 25(OH)D concentrations were compared between dogs with SHPT and those with normal PTH concentrations. RESULTS: Concentrations of iMg were weakly negatively correlated with PTH (rho, −.31; P = .03), and weakly positively correlated with serum 25(OH)D (rho, .34, P = .02) and iCa (rho, .42, P = .003). Ionized magnesium concentrations were lower in dogs with abnormally low 25(OH)D and SHPT compared to dogs with abnormally low 25(OH)D and normal parathyroid hormone concentrations (P = .01). CONCLUSIONS AND CLINICAL IMPORTANCE: Hypomagnesemia might contribute to alterations in iCa and parathyroid hormone in dogs with CE +/− PLE and abnormally low 25(OH)D.