title: Significant gender difference in serum levels of fibroblast growth factor 21 in Danish children and adolescents.
abstract: BACKGROUND
  Fibroblast Growth Factor 21 (FGF21) is a novel metabolic factor with effect on glucose and lipid metabolism, and shown to be elevated in diseases related to metabolic syndrome. Due to the increasing frequency of metabolic syndrome in the pediatric population, and as FGF21 studies in children are limited, we investigated baseline serum levels of FGF21 in healthy children during an oral glucose tolerance test.
  
  
  METHODS
  A total of 179 children and adolescents from the COPENHAGEN Puberty Study were included. An OGTT with glucose and insulin measurements, a dual energy X-ray absorptiometry (DXA) scan and a clinical examination including pubertal staging were done on all subjects. Serum levels of FGF21, adiponectin, and leptin were determined by immunoassays at baseline.
  
  
  RESULTS
  The girls had significantly higher levels of FGF21 compared with boys (155 pg/mL vs. 105 pg/mL, P = 0.04). 38 children (21%) had levels below detection limit of assay. Baseline levels of FGF21 showed positive correlation with triglycerides, but no significant correlations were found between FGF21-concentration and body mass index (BMI), DXA-derived fat percentage, LDL- HDL- and non-HDL cholesterol, leptin or adiponectin levels, respectively. Neither was any correlation found between baseline FGF21-levels and the dynamic changes in glucose and insulin levels during the OGTT.
  
  
  CONCLUSIONS
  FGF21 is independent of adiposity in children, and the significant metabolic effect seems to be limited to pathological conditions associated with insulin resistance. The higher levels of triglycerides in the girls may explain the significantly higher levels of FGF21 in girls compared with boys.
  
  
  BACKGROUND
  The COPENHAGEN Puberty Study was registered in ClinicalTrials.gov (identifier NCT01411527), and approved by the local ethics committee (reference no. KF 01 282214 and KF 11 2006-2033).
authors.affiliation: Department of Growth and Reproduction, Rigshospitalet, Copenhagen University Hospital, section 5064 Blegdamsvej 9, DK-2100 Copenhagen, Denmark ; Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Amalie
authors.initials: A
authors.lastname: Bisgaard
authors.affiliation: Department of Growth and Reproduction, Rigshospitalet, Copenhagen University Hospital, section 5064 Blegdamsvej 9, DK-2100 Copenhagen, Denmark ; Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Kaspar
authors.initials: K
authors.lastname: Sørensen
authors.affiliation: Department of Growth and Reproduction, Rigshospitalet, Copenhagen University Hospital, section 5064 Blegdamsvej 9, DK-2100 Copenhagen, Denmark ; Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Trine Holm
authors.initials: TH
authors.lastname: Johannsen
authors.affiliation: Department of Biomedical Sciences, Xlab, Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Jørn Wulff
authors.initials: JW
authors.lastname: Helge
authors.affiliation: Department of Growth and Reproduction, Rigshospitalet, Copenhagen University Hospital, section 5064 Blegdamsvej 9, DK-2100 Copenhagen, Denmark ; Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Andersson
authors.affiliation: Department of Growth and Reproduction, Rigshospitalet, Copenhagen University Hospital, section 5064 Blegdamsvej 9, DK-2100 Copenhagen, Denmark ; Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Juul
keywords: Fibroblast growth factor 21; Metabolic syndrome; Oral glucose tolerance test