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.