title: Secular trends in pubertal development.
abstract: OBJECTIVE
  To describe the secular trend in pubertal development in relation to the secular trend in height.
  
  
  METHODS
  Literature review of cross-sectional, longitudinal and twin studies.
  
  
  RESULTS
  Globally, there is a secular trend in adolescent growth for an increased mean final height at adulthood. To a lesser extent, there is also a secular trend towards earlier puberty. However, it seems that the two trends are not strongly connected. The increase in average height over the generations can, to a large extent, be explained by an earlier onset of the growth hormone-dependent phase of growth in early life. The age when this growth 'spurt' occurs in childhood strongly correlates with final height, but is not related to the age at peak height velocity during puberty. There is a large variation in the timing of the onset of puberty; it is largely influenced genetically, as implied by studies in twins. The single environmental factor that stands out as most significant - possibly explaining as much as 25% of the variation in the timing of puberty - is simply nutritional status in childhood; overnutrition and obesity seem to trigger pubertal onset. However, recent studies have identified that both shortness and thinness at birth are also associated with earlier pubertal maturation - a reverse of their impact during childhood years.
  
  
  CONCLUSIONS
  More longitudinal studies are needed to understand the short- and long-term consequences of secular changes in both final height and pubertal development before we know how important the trends are.
authors.affiliation: Clinical Trials Centre, University of Hong Kong, PR China. jpekarl@hkucc.hku.hk
authors.forename: Johan
authors.initials: J
authors.lastname: Karlberg
mesh_terms: D000293:Adolescent; D000367:Age Factors; D001827:Body Height / Q000502:physiology*; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004777:Environment; D005260:Female; D006801:Humans; D007223:Infant; D008137:Longitudinal Studies; D008297:Male; D011627:Puberty / Q000502:physiology*; D012727:Sex Characteristics; D012741:Sexual Maturation / Q000235:genetics / Q000502:physiology*; D018433:Twin Studies as Topic