Growth in Preterm Infants Until Six Months Postterm: The Role of Insulin and IGF-I

Since insulin-like growth factor type I (IGF-I) and insulin regulate growth in term infants, they were studied in relation to nutrient intake and growth until 6 months corrected age (CA) in preterm infants. In 138 preterm infants (51% male, gestational age (expressed as median (IQR)) 30.6 (1.9) weeks, birth weight 1,368 (389) g) weight SDS, length SDS, IGF-I, and insulin were measured at term age, 3 and 6 months CA. IGF-I and insulin at term age were associated with weight SDS and length SDS at term age and 3 months CA. IGF-I and insulin at 3 months CA were associated with weight SDS and length SDS at 3 and 6 months CA. IGF-I and insulin at term age were negatively associated with gain in weight SDS and gain in length SDS between term age and 6 months CA (IGF-I: β = -1.03, 95% CI -1.65;-0.41, p = 0.001 and β = -0.78, 95% CI -1.32;-0.23, p = 0.005; insulin: β = -0.19, 95% CI -0.37;-0.01, p = 0.044 and β = -0.18, 95% CI -0.35;-0.01, p = 0.035). Nutrient intake was not associated with IGF-I or insulin. The present study suggests that IGF-I and insulin are important growth regulators in preterm infants until 6 months CA, independent of nutrient intake