IGF-1 was measured with the IMMULITE 2000 solid-phase, enzyme-labeled chemiluminescent immunometric assay (Siemens Healthcare Diagnostic Products Limited, UK); normal age-appropriate ranges are as follows: 1–6 years: 49–327 μg/l; 7–11 years: 57–551 μg/l; 12–13 years: 143–850 μg/l; 14–16 years: 220–996 μg/l; 17–18 years: 163–731 μg/l; 19–20 years: 127–483 μg/l; 21–35 years: 115–358 μg/l; 36–50 years: 94–284 μg/l; >50 years: 55–238 μg/l; intra-assay CV: 2.3–3.5%; interassay CV: 7.0–7.1%; and sensitivity: 20 μg/l. IGF-1 index = IGF − 1/upper limit of normal range (ULN) [24 (link)].
Insulin was measured by chemiluminescence immunoassay (ADVIA Centaur XP, Siemens, USA). BG was measured by a Hitachi 7600 Biochemical Analyzer (Tokyo, Japan). HbA1c was detected with high-performance liquid chromatography (Tosoh HLC-723 G8 HPLC Analyzer, Japan).