Higher prepubertal IGF-1 concentrations associate to earlier pubertal tempo in both sexes

Introduction: Pubertal onset is triggered by multiple neuroendocrine interactions. The role of prepubertal IGF-1 in this process has not been explored in both sexes. Our objective is to analyze the association of prepubertal IGF-1 concentration with age at thelarche (B2) and menarche (M) in girls and age at gonadarche (G2) in boys.
Methods: Longitudinal study (n=1196 boys and girls) within the Growth and Obesity Chilean cohort Study (GOCS). At ages ≈ 6.7 years blood sample for IGF-1. Subjects analyzed into 4 groups according to the onset age of the pubertal event. 
Results: Higher prepubertal IGF-1 levels were observed at earlier ages of thelarche (p=0.003) and menarche onset (p=0.041). A taller prepubertal height was observed at younger ages of thelarche and menarche (p=<0.001 and 0.002, respectively).
The proportional hazard regression (HR) models showed that with an increase of 1 SD in IGF-1, the HR of presenting thelarche at younger ages was 1.25 and this association was maintained when adjusted for confounding variables. Similarly, the HR of presenting menarche at earlier ages was 1.21. This association was maintained only when adjusting for BMI but not using further confounders. In boys, prepubertal IGF-1 showed a tendency to be significantly higher in children with earlier gonadarche and taller height (both p<0.001). The HR of presenting gonadarche at younger ages was 1.22 and this association was maintained after adjusting for confounders.
Conclusions: higher IGF-I levels in mid-childhood are associated with earlier puberty onset. The role of IGF-I in the onset of puberty requires further investigation.
