17 General introduction 1 Study design The NUTRIE study, a longitudinal cohort study, was conducted between August 2015 andAugust 2018. The primary objective of this studywas to study the endocrine regulation of preterm growth and body composition. Secondary objectives were to study the influence of the endocrine regulation and early nutritional intake on neurodevelopmental outcome, bonemineralization, lipidprofileandbloodpressure in preterm infants. To detect a medium size effect (r = 0.35) of IGF-I concentration on fat mass percentage a sample size of at least 62 infants was required (power 80%, significance 5%). With an expected dropout rate of 10% drop out rate, the aim was to include 70 patients. Infants admitted to the neonatal intensive care unit (NICU) of the AmsterdamUMC - location VU University Medical Center were assessed for eligibility if they were born at a gestational age of 24 weeks + 0/7 days up to and including 31 weeks + 6/7 days. Infants who had substantial congenital abnormalities were excluded. Informed consent was obtained within the first week of life. Ninety patients were enrolled in the study. (Figure 1) Study participants were followed-up until 2 years corrected age. Anthropometric measures and endocrine parameters were registered during hospital stay as well as at follow-up. Body composition and bone mineral density were assessed at term age and 3, 6, 12, and 24 months corrected age, using air displacement plethysmography (PEA POD®/BOD POD®) and Dual Energy X-ray Absorptiometry (DXA). (Figure 2 and Figure 3) In addition cord blood analysis of infants with a gestational age of 24 to 42 weeks born at the VU University Medical Center in the study period took place to establish neonatal reference ranges for IGF I, IGF BP 3, Insulin, C-peptide, glucose, cortisol, cortisone and lipid profiles. (Figure 2 and Figure 3)
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