title: [Twin study of free insulin-like growth factor-1 on female pubertal development].
abstract: OBJECTIVE
  To explore the effect of insulin-like growth factor-1 (IGF-1) on female pubertal development and estimate heritability of the serum free IGF-1.
  
  
  METHODS
  The study population consisted of 427 girls aged 6 to 18 years: 132 pairs monozygotic twins, 48 pairs same-sex dizygotic twins and 67 girls with opposite-sex twin, who were all from Qingdao city, Shan-dong province. Their breast development were examined by Tanner standard and fast serum free IGF-1 contents were assayed by immunoradiometric assay (IRMA).
  
  
  RESULTS
  Serum free IGF-1 concentration increased firstly and decreased later throughout puberty. The peak of free IGF-1 was 12 years old, which equals to Tanner B2. Free IGF-1 heritability of group stage B1, B2-B5, pre-menarche and post-menarche were 0.53, 0.85, 0.48, 0.83 respectively, non-classed heritability was 0.53.
  
  
  CONCLUSIONS
  Fast increase of serum free IGF-1 before 12 years might be a predictor of the growth spurt and breast development. Genetic effect on female serum free IGF-1 was significant in the process of puberty.
authors.affiliation: Institute of Child and Adolescent Health, Peking University, Beijing 100083, China.
authors.forename: Hong-Juan
authors.initials: HJ
authors.lastname: Li
authors.forename: Cheng-Ye
authors.initials: CY
authors.lastname: Ji
authors.forename: Ye-Peng
authors.initials: YP
authors.lastname: Yang
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D011627:Puberty / Q000097:blood*; D012741:Sexual Maturation / Q000235:genetics* / Q000502:physiology
chemical_list: D007334:Insulin-Like Growth Factor I