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Insulin-like growth factor (IGF)-I and IGF-binding protein 3 during the first year in term and preterm infants
S Rajaram1, S E Carlson, W W Koo
1Department of Pediatrics, University of Tennessee, Memphis 38163, USA.
Insights
This study tracked Insulin-like Growth Factor-I (IGF-I) and IGF-binding protein 3 (IGFBP-3) in term and preterm infants. Preterm infants showed distinct IGF-I and IGFBP-3 patterns throughout their first year, influenced by gestational age.
Area of Science:
- Pediatric Endocrinology
- Neonatal Physiology
- Growth Factor Biology
Background:
- Insulin-like Growth Factor-I (IGF-I) and IGF-binding protein 3 (IGFBP-3) are crucial for infant growth.
- Understanding their dynamics in preterm infants is vital for assessing developmental trajectories.
Purpose of the Study:
- To compare plasma IGF-I and IGFBP-3 levels between term and preterm infants during the first year of life.
- To investigate the influence of gestational age and postnatal age on these growth factors.
Main Methods:
- Radioimmunoassay was used to measure plasma IGF-I and IGFBP-3.
- Study included 51 term and 51 preterm infants with serial measurements from before term to 12 months corrected age.
- Repeated measures analysis of variance and Fisher's least squares difference were employed for statistical analysis.
Main Results:
- Preterm infants exhibited significant fluctuations in IGF-I levels throughout the first year.
- IGFBP-3 levels in preterm infants showed a modest initial rise followed by a plateau.
- While similar at birth, preterm infants had higher IGF-I from 2-12 months and varied IGFBP-3 levels compared to term infants.
Conclusions:
- Both postnatal age and gestational age significantly influence IGF-I and IGFBP-3 levels in the first year.
- Gestational age impacts IGF-I and IGFBP-3 trajectories even after accounting for early birth, suggesting long-term effects.
Abstract:
Plasma IGF-I and IGF-binding protein 3 (IGFBP-3) were determined by radioimmunoassay in term infants (n = 51) at 0, 2, 4, 6, and 12 mo and preterm infants (n = 51) at -3 (28.4 wk postconceptional age), -2, -1.5, -1, 0, 2, 4, 6, 9, and 12 mo from expected term. The effects of gestational age at birth (term or preterm) and study age were determined by repeated measures analysis of variance and Fisher's least squares difference. In preterm infants, IGF-I increased between -3 and 2 mo from 0.75 to 10.4 nM, decreased between 2 and 9 mo to 7.3 nM, and increased again between 9 and 12 mo to 10.1 nM (p < 0.0001), whereas IGFBP-3 increased relatively little from -3 to 0 mo (14.2 to 30.2 nM, p < 0.05) and plateaued from 2 to 12 mo (49.8 to 62.3 nM). At 0 mo, IGF-I and IGFBP-3 were the same in term and preterm infants, but preterm infants had higher IGF-I from 2 through 12 mo (p < 0.05), higher IGFBP-3 at 2 and 4 mo (p < 0.05), and lower IGFBP-3 at 12 mo (p < 0.05). IGF-I and IGFBP-3 were correlated at most ages. First year IGF-I and IGFBP-3 are influenced by study age and by gestational age, even after adjusting for early birth.