Fibroblast growth factor 23 in feline chronic kidney disease.

Abstract

BACKGROUND: Fibroblast growth factor 23 (FGF-23) is a phosphaturic hormone involved in the pathogenesis of secondary renal hyperparathyroidism (SRHP) in humans. There are no published studies examining feline FGF-23. OBJECTIVES: Validation of a method for FGF-23 quantification in feline plasma and assessment of the associations among plasma FGF-23, PTH, creatinine, and phosphate concentrations in cats with chronic kidney disease (CKD). ANIMALS: One hundred nonazotemic and azotemic geriatric (>9&#xa0;years) client-owned cats. METHODS: Retrospective cross-sectional study: Cats were categorized into 4 groups: control group (plasma creatinine (Cr) &#x2264;2.0&#xa0;mg/dL), stage 2 (Cr 2.1-2.8&#xa0;mg/dL), stage 3 (Cr 2.9-5.0&#xa0;mg/dL), stage 4 (Cr >5.0&#xa0;mg/dL). Stages 2 and 3 were further subdivided based on International Renal Interest Society targets for plasma phosphate concentration (PO4 ): stage 2a (PO4 &#x2264;4.5&#xa0;mg/dL), stage 2b (PO4 >4.5&#xa0;mg/dL), stage 3a (PO4 &#x2264;5&#xa0;mg/dL), stage 3b (PO4 >5&#xa0;mg/dL). Plasma FGF-23 concentrations were measured by a human intact FGF-23 ELISA. Descriptive statistics and linear regression were performed. RESULTS: The ELISA demonstrated acceptable precision, reproducibility, and specificity. Plasma FGF-23 concentrations increased with increasing plasma creatinine concentrations and were significantly different between all groups (P&#xa0;<&#xa0;.008). Plasma FGF-23 concentrations were significantly higher in cats in stage 2b than stage 2a (P&#xa0;=&#xa0;.008) and in stage 3b than in stage 3a (P&#xa0;=&#xa0;.012). Phosphate, log creatinine, total calcium, log parathyroid hormone, and packed cell volume were all independent predictors of FGF-23. CONCLUSIONS AND CLINICAL IMPORTANCE: FGF-23 concentrations increase with increasing stage of feline CKD and might be a marker or mediator of feline SRHP.