Fibroblast Growth Factor 23 (FGF-23) Concentrations in Cats with Early Nonazotemic Chronic Kidney Disease (CKD) and in Healthy Geriatric Cats

Background Fibroblast growth factor (FGF-23) has an important role in phosphate regulation. Its clinical relevance in cats with CKD has not been explored previously. Hypothesis/Objectives The study objectives were (1) to determine whether FGF-23 concentrations are increased in nonazotemic cats, cats which developed azotemia within 12months of screening compared with cats that remained non-azotemic, and (2) to evaluate the relationships between FGF-23 and PTH and FGF-23 and glomerular filtration rate (GFR). Animals Sixty-two healthy client-owned geriatric cats, 14 of which developed azotemia during the 12-month follow-up period. Methods Healthy nonazotemic cats were recruited prospectively into the study and followed for 12months. At the study end-point, cats were categorized into 3 groups according to plasma creatinine concentration. PTH, FGF-23, and additional biochemical variables were evaluated at baseline and after 12months. GFR was measured by a corrected slope-intercept iohexol clearance method. Results FGF-23 concentrations at baseline were found to be significantly increased in cats that developed azotemia (P=.001) compared with cats that did not develop azotemia. A significant positive relationship was identified between FGF-23 and PTH, whereas the relationship between FGF-23 and GFR was negative. Conclusions and Clinical Importance FGF-23 concentrations predicted development of azotemia in geriatric cats. Positive relationships between FGF-23 and PTH suggest an association between FGF-23 and renal secondary hyperparathyroidism.