Normative data for insulin-like growth factor-1 (IGF-1) in healthy children and adolescents from India.

BACKGROUND: Serum IGF-1 is an important biochemical tool to diagnose and monitor GH-related disorders. However, ethnic-specific Indian data following consensus criteria for the establishment of normative data, are not available. Our objective was to generate chronological age (CA)-, bone age (BA)- and Tanner stage-specific normative data for IGF-1 in healthy Indian children and adolescents. METHODS: A cross-sectional epidemiological study was conducted in schools and the community, which enrolled apparently healthy children and adolescents with robust exclusion criteria. The outcome measure was serum IGF-1 assessed using an electro-chemiluminescence immunoassay (ECLIA). The 2.5th, 5th, 10th, 25th, 50th (median), 75th, 90th, 95th, and 97.5th centiles for IGF-1 were estimated using generalized additive models. RESULTS: We recruited 2226 apparently healthy participants and following exclusion, 1948 (1006 boys, 942 girls) were included in the final analysis. Girls had median IGF-1 peak at CA of 13 years (321.7 ng/mL), BA of 14 years (350.2 ng/mL) and Tanner stage IV (345 ng/mL), while boys had median IGF-1 peak at CA of 15 years (318.9 ng/mL) BA of 15 years (340.6 ng/mL) and Tanner stage III (304.8 ng/mL). Girls had earlier rise, peak and higher IGF-1 values. The reference interval (2.5th-97.5th percentile) was broader during peri-pubertal ages, indicating a higher physiological variability. CONCLUSION: This study provides ethnicity-specific normative data on serum IGF-1 and will improve the diagnostic utility of IGF-1 in the evaluation and management of growth disorders in Indian children and adolescents.