PURPOSE: The purpose of this test was to investigate the changes of serum IGF-1 and IGFBP-3 levels during a one-year gonadotropin releasing hormone agonist (GnRHa) treatment in central precocious puberty (CPP) girls. METHODS: From 2007 to 2009, 26 girls were enrolled in this study. They were diagnosed as having central precocious puberty and were treated with GnRHa (leuprolide actete) for one year. Their height, bone age, and serum IGF-1 and IGFBP-3 levels were evaluated every six months. RESULTS: At the time of diagnosis, their mean serum IGF-1 and IGFBP-3 levels were 302.90+/-102.54 ng/mL and 3,103.58+/-705.08 ng/mL, respectively. At six month after treatment, the serum IGF-1 and IGFBP-3 levels were slightly decreased. One year later, IGF-1 concentrations were higher than before treatment and IGFBP-3 levels were lower (P=NS). This result, however, was not statistically significant. CONCLUSION: Gonadal suppression with gonadotropin releasing hormones inversely influenced circulating IGF-1 and IGFBP-3 levels. However, the serum IGF-1 and IGFBP-3 levels were maintained at relatively steady levels, preserving a normal height velocity.