FGF23 and left ventricular hypertrophy: Increased FGF-23 concentrations have been independently associated with faster progression of CKD, and treatment-resistant secondary HPTH.112 Higher concentration of serum phosphorus (even if within the reference interval) and FGF-23 have been associated with increased mortality in all stages of CKD.113 This is most likely related to increased vascular calcification and left ventricular hypertrophy as a result of increased FGF-23.114 However, there have been no studies yet in dogs to evaluate circulating FGF-23 concentrations in CKD.