title: The association of FGF23 levels in obese adolescents with insulin sensitivity.
abstract: BACKGROUND
  The fibroblast growth factor 23 (FGF23) is the most important hormonal regulator of circulating phosphate levels. Apart from this essential role, it may also act as a 'hormone-like' factor involved in glucose and lipid metabolism. It is believed to have a potential role in the development of insulin resistance.
  
  
  OBJECTIVE
  The aim of the study was to compare FGF23 levels between two groups of obese adolescents: insulin resistant and non-insulin resistant.
  
  
  METHODS
  The study included 36 obese, insulin-resistant adolescents (21 boys and 15 girls) of pubertal age (mean age, 13.95 years; Tanner stage IV or V). The control group consisted of 21 obese peers with normal HOMA-IR values.
  
  
  METHODS
  FGF23 levels were measured in a fasting blood sample by Human Intact FGF-23 ELISA Kit (Immunotopics Inc., San Clemente, CA, USA). A standard oral glucose tolerance test was performed, which assessed fasting and 120 min postload plasma glucose and serum insulin levels; the insulin resistance index HOMA-IR was calculated. The definition of insulin resistance was based on a HOMA-IR threshold set for adolescents (> or = 3.16).
  
  
  RESULTS
  There was a significant inverse correlation between FGF23 levels and HOMA-IR (R = -0.26, p < 0.05) in the study group. FGF23 levels were also significantly lower in the study group (9.8 vs. 11.9 pg/mL, p = 0.026).
  
  
  CONCLUSIONS
  In adolescents with simple obesity and insulin resistance, FGF23 levels are lower compared with obese adolescents with normal HOMA-IR.
authors.affiliation: Pediatric and Adolescent Endocrinology Department, Chair of Pediatrics, Jagiellonian University, Collegium Medicum, Wielicka St. 265, 30-663 Krakow, Poland. wojcik.gosia@gmail.com
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Wojcik
authors.forename: Dominika
authors.initials: D
authors.lastname: Janus
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Dolezal-Oltarzewska
authors.forename: Dorota
authors.initials: D
authors.lastname: Drozdz
authors.forename: Krystyna
authors.initials: K
authors.lastname: Sztefko
authors.forename: Jerzy B
authors.initials: JB
authors.lastname: Starzyk
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D001823:Body Composition / Q000502:physiology; D016022:Case-Control Studies; D002648:Child; D002784:Cholesterol / Q000097:blood; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D009765:Obesity / Q000097:blood* / Q000453:epidemiology / Q000378:metabolism / Q000503:physiopathology
chemical_list: D001786:Blood Glucose; C000717427:FGF23 protein, human; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002784:Cholesterol