Reference ranges for serum IGF-1 and IGFBP-3 levels in Chinese children during childhood and adolescence.

Serum levels of insulin-like growth factor-1(IGF-1) and insulin-like growth factor binding protein-3(IGFBP-3) reflect endogenous growth hormone secretion, and serum IGF-1 and IGFBP-3 values should be ethnic-specific, thus we established the reference ranges for serum IGF-1 and IGFBP-3 in Chinese children aged 6-18 yr according to age, sex, puberty stage and BMI. The study was included 837 children (age 6-18 yr, 416 boys and 421 girls) from different schools in Daqing, Beijing and Shanghai. Serum IGF-1 and IGFBP-3 were determined by a chemiluminescent assay system (IMMULITE 1000). The results show that IGF1 reached peak levels at around 13 yr in boys and 11 yr in girls while IGFBP-3 peaked at 14 yr in boys, and 11 yr in girls. Both IGF-1 and IGFBP-3 were at platform or decreased slightly after these ages. At each corresponding age, IGF-1 levels tended to be higher in boys compared to girls, while girls had higher IGFBP-3 levels than boys. A model for calculation of standard deviation scores of IGF-1 and IGFBP3 according to age, sex and pubertal stage was established. These normative data should facilitate child care, growth monitoring, clinical diagnosis and to follow up on GH treatment.