title: Pathophysiological implications of fibroblast growth factor-23 and Klotho and their potential role as clinical biomarkers.
abstract: BACKGROUND
  Fibroblast growth factor-23 (FGF-23) and Klotho constitute the main regulatory system of phosphorus homeostasis. Beyond this physiological role, there is growing evidence suggesting that this system has relevant pathophysiological implications in different clinical processes.
  
  
  BACKGROUND
  In this review we discuss the pathophysiological implications of the FGF-23/Klotho system and the potential utility that measurements of its components may have as clinical biomarkers in different clinical settings, such as progression of chronic kidney disease, acute renal failure, and secondary hyperparathyroidism, as well as vascular dysfunction, atherosclerosis, and cardiovascular morbidity and mortality. We outline and discuss the current commercially available assays for determination of FGF-23 and Klotho and the assay limitations that must be overcome to translate these biomarkers into reliable indicators in clinical practice.
  
  
  CONCLUSIONS
  In addition to its physiological role, the FGF-23/Klotho system appears to provide important information regarding the pathophysiology of several clinical conditions. Although there has been increasing study of the components of this new biological system and their potential use as clinical biomarkers, the ultimate value of this system in clinical practice will not be known until remaining assay limitations can be overcome and adequately designed studies have been conducted to demonstrate its clinical utility.
authors.affiliation: Research Unit, GEENDIAB and REDINREN (Sociedad Española de Nefrología e Instituto de Salud Carlos III, RD12/0021/0019), Madrid, Spain.
authors.forename: Javier
authors.initials: J
authors.lastname: Donate-Correa
authors.affiliation: Clinical Analysis Service, and GEENDIAB and REDINREN (Sociedad Española de Nefrología e Instituto de Salud Carlos III, RD12/0021/0019), Madrid, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Muros de Fuentes
authors.affiliation: Research Unit, GEENDIAB and REDINREN (Sociedad Española de Nefrología e Instituto de Salud Carlos III, RD12/0021/0019), Madrid, Spain.
authors.forename: Carmen
authors.initials: C
authors.lastname: Mora-Fernández
authors.affiliation: Research Unit, Nephrology Service, University Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain; GEENDIAB and REDINREN (Sociedad Española de Nefrología e Instituto de Salud Carlos III, RD12/0021/0019), Madrid, Spain. jnavgon@gobiernodecanarias.org.
authors.forename: Juan F
authors.initials: JF
authors.lastname: Navarro-González
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis / Q000378:metabolism; D015415:Biomarkers / Q000032:analysis / Q000378:metabolism*; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000378:metabolism / Q000401:mortality; D004797:Enzyme-Linked Immunosorbent Assay; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000032:analysis / Q000378:metabolism*; D005966:Glucuronidase / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000175:diagnosis / Q000378:metabolism; D000090265:Klotho Proteins; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis / Q000378:metabolism
chemical_list: D015415:Biomarkers; C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D005966:Glucuronidase; D000090265:Klotho Proteins