Biochemical growth marker assessments
At each follow-up, blood samples were collected and measured for serum insulin-like growth factor 1 (IGF-1) and IGF-binding protein 3 (IGFBP-3) levels at a central laboratory. Both serum IGF-1 and IGFBP-3 were measured by enzyme-labeled chemiluminescent immunometric assays (IMMULITE 2000; Siemens Healthcare Diagnostics Products Limited). IGF-1 SDS was calculated after adjusting for age and gender according to the reference published by Isojima et al. [