Korean Journal of Pediatrics 2008;51(1):47-53.
Published online January 15, 2008.
Serum levels of free insulin-like growth factor-I and clinical value in healthy children
Young Hee Chung, Woo Yeong Chung
Department of Pediatrics, College of Medicine, Inje University, Busan, Korea
한국 소아 및 청소년에서 혈중 유리 insulin-like growth factor-I농도치와 임상적 의의
정영희, 정우영
인제대학교 의과대학 소아과학교실
Correspondence: 
Woo Yeong Chung, Email: chungwy@chollian.net
Abstract
Purpose
: The serum levels of total insulin-like growth factor (IGF)-I and IGF binding protein (IGFBP)- 3 reflect endogenous growth hormone (GH) secretion in healthy children. Free form of IGF-I which is suggested to have more potent biological action than complex form of IGF-I. The aim of this study is to investigate the serum levels of free IGF-I and its clinical value in healthy children.
Methods
: Serum levels of total IGF-I and IGFBP-3 were determined in 494 healthy children (248 boys and 246 girls) by RIA and IRMA. Serum level of free IGF-I was determined in 206 healthy children (103 boys and 103 girls) by IRMA.
Results
: The free IGF-I level increased with age in both sex. The free IGF-I level increased continuously between 7 and 15 years of age in boys, but decrement was noted after 14 years of age in girls. Serum total IGF-I level also increased with age in similar pattern of that of free IGF-I. There were no significant differences of mean values of the ratio of free IGF-I/total IGF-I in relation to age in both sex. And there were significant correlations between the level of free IGF-I and total IGF-I and the ratio of total IGF-I/IGFBP-3, respectively.
Conclusion
: In healthy children, serum free IGF-I increased with age in both sex and high free IGF-I level may play an important role in pubertal growth spurt. Our results suggest that the increased serum free IGF-I level in puberty may reflect changes in total IGF-I rather than IGFBP-3. But free IGF-I does not have more clinical value than total IGF-I because of no significant differences of mean values of the ratio of free IGF-I/total IGF-I in relation to age.
Key Words: Free insulin-like growth factor-I, Total insulin-like growth factor-I, Insulin-like growth factor binding protein-3, Pubertal growth, Clinical value


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