Circulating IGF-I Levels in Childhood Are Related to Both Current Body Composition and Early Postnatal Growth Rate

Rapid infancy growth predicts childhood obesity and earlier rate of maturation. We examined whether early growth rates might also influence levels of hormones relating to growth and weight gain by measuring IGF-I, IGF-II, and leptin levels in 497 normal 5-yr-old children who were followed closely from birth. IGF-I levels at 5 yr were unrelated to cord blood IGF-I levels at birth (r = 0.03; P = 0.7; n = 166) but were positively related to current weight (r = 0.32; P 0.67 SD score) had higher IGF-I levels than other children (P = 0.02). IGF-II levels at 5 yr were positively related to IGF-II levels at birth (r = 0.17; P = 0.03; n = 166), and leptin levels at 5 yr were mainly related to current adiposity. Circulating IGF-I levels in childhood are influenced by infancy growth rates and possibly mediate the effects of early postnatal nutrition on later rates of growth and maturation.