Fibroblast growth factor-23 as an early marker of CKD-mineral bone disorder in dogs: preliminary investigation

OBJECTIVES To examine the relationship between fibroblast growth factor-23 levels, chronic kidney disease severity and mineral metabolic disorders associated to chronic kidney disease in dogs. MATERIALS AND METHODS Fifteen control and 75 chronic kidney disease dogs were retrospectively included. Serum fibroblast growth factor-23 concentration and other phosphate metabolite parameters were compared between controls and each International Renal Interest Society stage. Multiple regression analysis was performed to determine the predictors of fibroblast growth factor-23. RESULTS Serum fibroblast growth factor-23 concentrations were significantly higher in dogs with IRIS stages 2, 3 and 4 chronic kidney disease than those in dogs in control group and with stage 1 and increased along with the severity of chronic kidney disease. Compared with control dogs, serum intact parathyroid hormone significantly increased from stage 2 and serum phosphorus concentrations increased in dogs with stage 4. In dogs with stage 2, fibroblast growth factor-23 levels significantly increased in those with hyperphosphatemia compared with those with normophosphatemia. While eight of 26 (30.8%) dogs with stage 2 developed hyperparathyroidism (intact parathyroid hormone>8.5 ng/L), 19 (73.1%) dogs with stage 2 had elevated fibroblast growth factor-23 levels above the reference range (>528 pg/mL). Log creatinine, log intact parathyroid hormone and log product of total calcium and phosphorus were independent predictors of log fibroblast growth factor-23. CLINICAL SIGNIFICANCE This preliminary study suggests that canine fibroblast growth factor-23 might be involved in mineral metabolic disorders associated to chronic kidney disease in dogs, and this factor could be potentially used as an early marker for this condition.