FGF23 and metabolic syndrome: There are numerous studies looking for predictors for the progression of CKD or ESRD aside from estimated GFR and proteinuria, including age, sex, ethnicity, hypertension, diabetes, dyslipidemia, hyperuricemia, hyperphosphatemia, and some novel biomarkers such as fibroblast growth factor 23 (FGF23), and ceruloplasmin.[34] FGF23 is highly expressed in bone.