title: The relationship between Insulin-like Growth Factor 1, sex steroids and timing of the pubertal growth spurt.
abstract: OBJECTIVE
  Progress through puberty involves a complex hormonal cascade, but the individual contributions of hormones, particularly IGF-1, are unknown. We reanalysed Chard growth study data to explore the tempo of puberty based on changes in both height and hormone levels, using a novel method of growth curve analysis.
  
  
  METHODS
  Schoolboys (n = 54) and girls (n = 70) from Chard, Somerset, England, recruited in 1981 at age 8/9 and followed to age 16.
  
  
  METHODS
  Every 6 months, height and Tanner stages (genitalia, breast, pubic hair) were recorded, and in a subsample (24 boys, 27 girls), blood samples were taken. Serum IGF-1, testosterone (boys) and oestradiol (girls) were measured by radioimmunoassay. Individual growth curves for each outcome were analysed using variants of the super-imposition by translation and rotation (SITAR) method, which estimates a mean curve and subject-specific random effects corresponding to size, and age and magnitude of peak velocity.
  
  
  RESULTS
  The SITAR models fitted the data well, explaining 99%, 65%, 86% and 47% of variance for height, IGF-1, testosterone and oestradiol, respectively, and 69-88% for the Tanner stages. During puberty, the variables all increased steeply in value in individuals, the ages at peak velocity for the different variables being highly correlated, particularly for IGF-1 vs height (r = 0·74 for girls, 0·92 for boys).
  
  
  CONCLUSIONS
  IGF-1, like height, the sex steroids and Tanner stages, rises steeply in individuals during puberty, with the timings of the rises tightly synchronized within individuals. This suggests that IGF-1 may play an important role in determining the timing of puberty.
authors.affiliation: Population Policy and Practice Programme, UCL Institute of Child Health, London, UK.
authors.forename: T J
authors.initials: TJ
authors.lastname: Cole
authors.affiliation: Department of Paediatrics, Children's Hospital, Oxford, UK.
authors.forename: M L
authors.initials: ML
authors.lastname: Ahmed
authors.affiliation: Genetics and Genomic Medicine Programme, UCL Institute of Child Health, London, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Preece
authors.affiliation: Developmental Endocrinology Research Group, UCL Institute of Child Health, London, UK.
authors.forename: P
authors.initials: P
authors.lastname: Hindmarsh
authors.affiliation: Department of Paediatrics, University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors.forename: D B
authors.initials: DB
authors.lastname: Dunger
mesh_terms: D000293:Adolescent; D041923:Adolescent Development / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D002648:Child; D004739:England; D004958:Estradiol / Q000097:blood*; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008137:Longitudinal Studies; D008297:Male; D011627:Puberty / Q000502:physiology*; D012741:Sexual Maturation / Q000502:physiology; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I