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Circulating insulin-like growth factor I levels in newborn premature and full-term infants followed longitudinally
Insights
Premature infants show reduced growth, with insulin-like growth factor I (IGF-I) levels correlating to gestational age. Full-term infants experience a distinct postnatal IGF-I surge, unlike premature infants.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Growth Factors
Background:
- Infants born prematurely often exhibit diminished growth compared to intrauterine standards.
- Insulin-like Growth Factor I (IGF-I) plays a crucial role in fetal and postnatal growth.
- Understanding IGF-I dynamics in premature infants is vital for assessing growth and development.
Purpose of the Study:
- To longitudinally measure circulating IGF-I levels in premature and full-term infants.
- To investigate the relationship between gestational age and postnatal IGF-I levels.
- To compare IGF-I profiles between appropriate-for-gestational age (AGA) and small-for-gestational age (SGA) infants.
Main Methods:
- Radioimmunoassay was used to measure IGF-I levels in serum or plasma.
- Subjects included premature infants (AGA and SGA) and full-term infants, categorized by gestational age at birth.
- Longitudinal measurements were taken from cord blood through several weeks postnatally.
Main Results:
- Premature infants demonstrated reduced growth and lower IGF-I levels compared to fetal estimates.
- Basal postnatal IGF-I levels in premature infants were primarily dependent on gestational age, increasing slowly post-birth.
- Full-term infants exhibited a significant postnatal surge in IGF-I between days 1 and 10-15, distinguishing them from early premature infants.
- No significant difference in cord IGF-I levels was observed between AGA and SGA infants in the 34-37 week gestational age cohort.
Conclusions:
- Gestational age is the primary determinant of basal postnatal IGF-I levels in premature infants.
- The distinct postnatal IGF-I surge in full-term infants suggests unique regulatory mechanisms post-birth.
- IGF-I monitoring may offer insights into growth trajectories and potential interventions for premature infants.
Abstract:
Longitudinal circulating levels of insulin-like growth factor I (IGF-I) were measured by radioimmunoassay after acid/ethanol extraction of serum or plasma in 44 appropriate-for-gestational age (AGA) premature infants, 7 small-for-gestational age (SGA) premature infants and 9 AGA full-term infants. The subjects were divided into cohorts with gestational age at birth 26-29 weeks, 30-33 weeks, 34-37 weeks and 38-42 weeks (full-term). The premature infants in this study exhibited diminished growth as compared with normal intrauterine growth. In all but the earliest premature infant cohort there was an immediate fall from the mean fetal IGF-I level, as reflected by the cord value, to a basal postnatal circulating level of IGF-I. The basal level of circulating IGF-I in premature infants was related only to gestational age. It increased slowly from 25 weeks gestation until four weeks after full-term equivalent and was independent of time of birth. Full-term infants were distinguished from early premature infants by the occurrence of a prominent postnatal surge in circulating IGF-I levels that was characterised by a significant (P less than 0.02) increase between day 1 and days 10-15. The SGA and AGA infants in the 34-37 week cohort showed similar profiles of circulating IGF-I with no significant difference in cord values between the two groups.