Association between serum fibroblast growth factor-23 concentrations and blood calcium levels in chronic kidney disease cats with upper urolithiasis.

Abstract

OBJECTIVES: This study investigated whether serum fibroblast growth factor (FGF)-23 concentrations are associated with serum total calcium (tCa) and blood ionised calcium (iCa) concentrations in cats with chronic kidney disease (CKD) and upper urolithiasis. METHODS: Serum samples and the medical records of cats with CKD with nephroliths, ureteroliths or both were investigated retrospectively. Cats with a serum creatinine concentration >250&#x2009;&#x3bc;mol/l and/or a serum phosphorus concentration &#x2a7e;1.50&#x2009;mmol/l were excluded. Based on cut-offs for serum tCa (2.70&#x2009;mmol/l) or blood iCa (1.40&#x2009;mmol/l), cats were divided into the following groups: total hypercalcaemia (H-tCa) (>2.70&#x2009;mmol/l) and total normocalcaemia (N-tCa) (&#x2a7d;2.70&#x2009;mmol/l) groups, or ionised hypercalcaemia (H-iCa) (>1.40&#x2009;mmol/l) and ionised normocalcaemia (N-iCa) (&#x2a7d;1.40&#x2009;mmol/l) groups, respectively. Serum FGF-23 concentrations were compared between groups and correlation analysis was performed. RESULTS: Thirty-two cats with CKD and upper urolithiasis were included. Serum FGF-23 concentrations in the H-tCa group (median 573&#x2009;pg/ml [range 125-3888]; n&#x2009;=&#x2009;12) were significantly higher compared with the N-tCa group (median 245&#x2009;pg/ml [range 94-627]; n&#x2009;=&#x2009;20) (&#x2009;=&#x2009;0.001). Serum FGF-23 concentrations in the H-iCa group (median 1479&#x2009;pg/ml [range 509-3888]; n&#x2009;=&#x2009;6) increased significantly compared with the N-iCa group (median 245&#x2009;pg/ml [range 94-637]; n&#x2009;=&#x2009;26) (<0.001). Serum FGF-23 concentrations significantly correlated with serum tCa (&#x2009;=&#x2009;0.511,&#x2009;=&#x2009;0.003) and blood iCa concentrations (&#x2009;=&#x2009;0.425,&#x2009;=&#x2009;0.015) but not serum creatinine (&#x2009;=&#x2009;0.279,&#x2009;=&#x2009;0.122) or phosphorus concentrations (&#x2009;=&#x2009;0.208,&#x2009;=&#x2009;0.253).Increased serum FGF-23 concentrations were associated with hypercalcaemia independently of creatinine and phosphate status in cats with CKD and upper urolithiasis.