title: Beta-cell replication is the primary mechanism subserving the postnatal expansion of beta-cell mass in humans.
abstract: OBJECTIVE
  Little is known about the capacity, mechanisms, or timing of growth in beta-cell mass in humans. We sought to establish if the predominant expansion of beta-cell mass in humans occurs in early childhood and if, as in rodents, this coincides with relatively abundant beta-cell replication. We also sought to establish if there is a secondary growth in beta-cell mass coincident with the accelerated somatic growth in adolescence.
  
  
  METHODS
  To address these questions, pancreas volume was determined from abdominal computer tomographies in 135 children aged 4 weeks to 20 years, and morphometric analyses were performed in human pancreatic tissue obtained at autopsy from 46 children aged 2 weeks to 21 years.
  
  
  RESULTS
  We report that 1) beta-cell mass expands by severalfold from birth to adulthood, 2) islets grow in size rather than in number during this transition, 3) the relative rate of beta-cell growth is highest in infancy and gradually declines thereafter to adulthood with no secondary accelerated growth phase during adolescence, 4) beta-cell mass (and presumably growth) is highly variable between individuals, and 5) a high rate of beta-cell replication is coincident with the major postnatal expansion of beta-cell mass.
  
  
  CONCLUSIONS
  These data imply that regulation of beta-cell replication during infancy plays a major role in beta-cell mass in adult humans.
authors.affiliation: Larry Hillblom Islet Research Center, UCLA David Geffen School of Medicine, Los Angeles, California 90095-7073, USA.
authors.forename: Juris J
authors.initials: JJ
authors.lastname: Meier
authors.forename: Alexandra E
authors.initials: AE
authors.lastname: Butler
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Saisho
authors.forename: Travis
authors.initials: T
authors.lastname: Monchamp
authors.forename: Ryan
authors.initials: R
authors.lastname: Galasso
authors.forename: Anil
authors.initials: A
authors.lastname: Bhushan
authors.forename: Robert A
authors.initials: RA
authors.lastname: Rizza
authors.forename: Peter C
authors.initials: PC
authors.lastname: Butler
mesh_terms: D000293:Adolescent; D000328:Adult; D000375:Aging / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D050417:Insulin-Secreting Cells / Q000166:cytology*; D009929:Organ Size; D010179:Pancreas / Q000166:cytology / Q000254:growth & development*