Insulin-like growth factor I concentrations in infancy predict differential gains in body length and adiposity: the Cambridge Baby Growth Study.
BACKGROUND
Formula milk-fed infants show faster rates of growth and weight gain than do breastfed infants, and they have higher concentrations of insulin-like growth factor I (IGF-I).


OBJECTIVE
Our objective was to determine the influence of IGF-I concentrations on gains in weight, length, body mass index (BMI), and adiposity in the first year of life.


METHODS
IGF-I concentrations were measured in 953 capillary blood samples from 675 unselected infants at ages 3 and 12 mo. These infants were born between 2002 and 2008 in one center and were participating in a prospective longitudinal birth cohort. Weight, length, and 4 skinfold thicknesses as an indicator of adiposity were measured at ages 0, 3, and 12 mo. Analyses were adjusted for age and sex.


RESULTS
Infants who were formula milk-fed had higher IGF-I concentrations at 3 mo, and they showed greater gains in weight, length, BMI, and adiposity between age 3 and 12 mo. IGF-I concentrations at 3 mo were unrelated to subsequent overall weight gain (P = 0.5). However, higher IGF-I concentrations at age 3 mo predicted greater subsequent gains in body length (P < 0.001 and P = 0.007 in formula milk-fed and breastfed infants, respectively) and slower gains in BMI (P < 0.001 and P = 0.004, respectively) and adiposity (P = 0.03 and P = 0.003, respectively).


CONCLUSIONS
Our findings support a key role for IGF-I in the partitioning of overall infant weight gain into statural growth compared with adiposity. In formula milk-fed infants, higher IGF-I concentrations may lead to faster gains in length; however, other mechanisms likely explain their faster gains in weight, BMI, and adiposity.
Ong
Ken K
KK
Medical Research Council Epidemiology Unit, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, UK. ken.ong@mrc-epid.cam.ac.uk
Langkamp
Markus
M
Ranke
Michael B
MB
Whitehead
Karen
K
Hughes
Ieuan A
IA
Acerini
Carlo L
CL
Dunger
David B
DB
D000273:Adipose Tissue / Q000033:anatomy & histology*; D000818:Animals; D001827:Body Height; D015992:Body Mass Index; D005260:Female; D006128:Growth / Q000502:physiology*; D006801:Humans; D007223:Infant; D041943:Infant Formula; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008137:Longitudinal Studies; D008297:Male; D008892:Milk; D012885:Skinfold Thickness; D015430:Weight Gain
D007334:Insulin-Like Growth Factor I