title: Longitudinal changes in insulin-like growth factor-I, insulin sensitivity, and secretion from birth to age three years in small-for-gestational-age children.
abstract: BACKGROUND
  Insulin resistance (IR) develops as early as age 1 to 3 yr in small for gestational age (SGA) infants who show rapid catch-up postnatal weight gain. In contrast, greater insulin secretion is related to infancy height gains. We hypothesized that IGF-I levels could be differentially related to gains in length and weight and also differentially related to IR and insulin secretion.
  
  
  METHODS
  In a prospective study of 50 SGA (birth weight < 5th percentile) and 14 normal birth weight [appropriate for gestational age (AGA)] newborns, we measured serum IGF-I levels at birth, 1 yr, and 3 yr. IR (by homeostasis model assessment) and insulin secretion (by short iv glucose tolerance test) were also measured at 1 yr and 3 yr.
  
  
  RESULTS
  SGA infants had similar mean length and weight at 3 yr compared with AGA infants. SGA infants had lower IGF-I levels at birth (P < 0.0001), but conversely they had higher IGF-I levels at 3 yr (P = 0.003) than AGA infants. Within the SGA group, at 1 yr IGF-I was associated with length gain from birth and insulin secretion (P < 0.0001); in contrast at 3 yr IGF-I was positively related to weight, body mass index, and IR.
  
  
  CONCLUSIONS
  IGF-I levels increased rapidly from birth in SGA, but not AGA children. During the key first-year growth period, IGF-I levels were related to beta-cell function and longitudinal growth. In contrast, by 3 yr, when catch-up growth was completed, IGF-I levels were related to body mass index and IR, and these higher IGF-I levels in SGA infants might indicate the presence of relative IGF-I resistance.
authors.affiliation: Institute of Maternal and Child Research, Faculty of Medicine, University of Chile, 1027 Santiago, Chile.
authors.forename: Germán
authors.initials: G
authors.lastname: Iñiguez
authors.forename: Ken
authors.initials: K
authors.lastname: Ong
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Bazaes
authors.forename: Alejandra
authors.initials: A
authors.lastname: Avila
authors.forename: Teresa
authors.initials: T
authors.lastname: Salazar
authors.forename: David
authors.initials: D
authors.lastname: Dunger
authors.forename: Verónica
authors.initials: V
authors.lastname: Mericq
mesh_terms: D001724:Birth Weight; D016022:Case-Control Studies; D002657:Child Development; D002675:Child, Preschool; D005951:Glucose Tolerance Test; D006801:Humans; D007223:Infant; D007230:Infant, Low Birth Weight / Q000097:blood; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000097:blood*; D007328:Insulin / Q000097:blood* / Q000378:metabolism*; D007333:Insulin Resistance; D000078790:Insulin Secretion; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D011446:Prospective Studies
chemical_list: D007328:Insulin; D007334:Insulin-Like Growth Factor I