FGF23 and chronic kidney disease: The serum FGF-23 levels were higher in the rats from the CKD + exercise group (723.9 ± 57.1 pg/mL) and the CKD group (836.1 ± 71.4 pg/mL) than those in the rats from the sham group (404.6 ± 64.8 pg/mL); this was because of the declined renal function in rats from the CKD and CKD + exercise groups (Figure 1A).