Analysis of the relationship of insulin-like growth factor-1 to the growth velocity and feeding of healthy infants

Context: Infancy is the fastest growth period in a child's development after birth, but little is known about hormonal regulation mechanism for the growth and development of this period.

Objective: The objective of this study is to analyze the trend of serum IGF-1 levels in healthy infants and the relationship of IGF-1 to the growth velocity and feeding method of infants.

Design: Population-based birth cohort study.

Setting: The study was conducted in the Third Hospital of Peking University.

Participants: Study participants were 484 healthy infants, all of whom were full-term and appropriate for gestational age (238 boys and 246 girls).

Interventions: Interventions were anthropometrical measurements, feeding methods recorded every 1 to 2 months and serum samples (2, 4, 6, 8, 10,12 months).

Main outcome measures: Height, weight, feeding methods and serum IGF-1 were the main outcome measures.

Results: Serum IGF-1 levels decreased in the following 2 months in boys but in females levels remained relatively high between 2 to 3 months after birth and then started to decrease. It reached the lowest point at Months 7-8, and was on a slow rise in both male infants and female infants thereafter. Serum IGF-1 levels were significantly higher in female infants [112.65 ng/ml (CI 91.82, 133.89)] than in male infants [74.38 ng/ml (CI 53.14, 95.61)] at early infancy. Infants fed with human milk had lower serum IGF-1 levels than infants fed with formula milk or human milk plus formula milk (66.94 ± 45.85 ng/ml, 72.56 ± 36.55 ng/ml, 79.89 ± 51.79 ng/ml, respectively; P = 0.019). IGF-1 levels were positively correlated to the growth velocity of body length (P<0.01).

Conclusion: This study provides the trend for IGF-1 levels at infancy. It is highly possible that IGF-1 plays an important role in the regulation and control of length increases in infants, and feeding method influences serum IGF-1 levels.