Moreover, elevated FGF-23 levels were found to predict rapid progression of kidney disease, and among patients with end-stage renal disease (ESRD) treated with dialysis, FGF-23 levels were associated with abnormal bone metabolism.(10) left ventricular hypertrophy and mass index,(11) vascular calcifications,(12) and increased mortality.(13,14) FGF-23 thus appears to have an important role as a biomarker in CKD patients, and measuring FGF-23 levels is likely to provide a sensitive diagnostic tool for assessing phosphate homeostasis and possibly its detrimental “off-target” effects. The gene discussed is FGF23; the disease is stage 5 chronic kidney disease.