Longitudinal changes in insulin-like growth factor-I, insulin sensitivity, and secretion from birth to age three years in small-for-gestational-age children.
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.
Iñiguez
Germán
G
Institute of Maternal and Child Research, Faculty of Medicine, University of Chile, 1027 Santiago, Chile.
Ong
Ken
K
Bazaes
Rodrigo
R
Avila
Alejandra
A
Salazar
Teresa
T
Dunger
David
D
Mericq
Verónica
V
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
D007328:Insulin; D007334:Insulin-Like Growth Factor I