FGF23 and chronic kidney disease: In a study of 3,879 CKD patients, a significant increase in FGF23 and PHT levels and a decrease in 1,25-dihydroxyvitamin D levels were evident at stage 3 CKD when estimated glomerular filtration rate (eGFR) ≤ 59 mL/min/1.73 m2 [66].