109 IGF-I, growth and body composition in preterm infants 5 In our study cohort a greater increase in IGF-I in the firstmonth of lifewas associated withmore fat freemass at termequivalent age. In addition, our results showed that less decrease in weight SDS in the first month of life was associated with a higher fat free mass percentage at term equivalent age. The change in length and head circumference SDS were not associated with body composition. Nevertheless, while a higher length SDS at 4 weeks postnatal age was associated with both a higher fat mass as well as a higher fat free mass, a higher head circumference SDS at 4 weeks postnatal age was associated with higher fat free mass alone. In line with our findings, Hernandez and colleagues found higher IGF-I levels in the first week of life to be associated with increased lean mass at 2 years corrected age in small for gestational age preterm infants. (10) Therefore, our results suggest that impaired growth in the first month of life, i.e. lower IGF-I levels and weight and head circumference SDS, is associated with a less favorable body composition at term equivalent age. Interestingly, we observed that the postnatal change in IGF-I was independent of gestational age at birth, i.e. the rate of increase of IGF-I depended on postmenstrual ageat the timeof bloodsampling regardless of thegestational ageat birth. Likewise, Hansen-Pupp and colleagues found IGF-I to increase at 30 weeks gestational age, irrespective of gestational age at birth(14) Accordingly, in our population IGF-I showed an increase from 31 weeks PMA. Taking into account that our findings suggest early IGF-I levels are important for a more favorable body composition, there may be a window of opportunity for interventions to increase IGF-I levels in this early phase. Indeed, trials with IGF-I administration between preterm birth and 30 weeks PMA show promising results with regards to the occurrence of major comorbidities such as BPD. However, IGF-I is expected to affect various organ systems. Current studies have not shown a decrease in other comorbidities such as ROP and the effects of IGF-I administration on body composition are yet to be investigated . (15) Furthermore, IGF-I administration is an invasive and burdensome procedure, which might limit its implementation in clinical practice. IGF-I levels and growth up to term equivalent age From birth to 36 weeks PMA and at term equivalent age there was still a positive, but weak, association between change in IGF-I and fat free mass. Nevertheless, there was no association with the change from30 weeks PMA onwards. Taking into account, the stronger association in thefirstmonthof life, it couldbe suggested that early changes in IGF-I are more important in influencing body composition at term equivalent age. Nevertheless, given the sample size and observational nature of this study, the evidence for this hypothesis is inconclusive and remains speculative. Moreover, this is in contrast to reports by Ruys and colleagues who found a positive association between IGF-I and fat free mass as well as fat mass measured in
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