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 was 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: This is a longitudinal study (n = 1,196 boys and girls) within the Growth and Obesity Chilean Cohort Study (GOCS). At age ≈ 6.7 years, blood sample was taken for IGF-1. Subjects were divided into 4 groups according to the onset age of the pubertal event. RESULTS: Higher prepubertal IGF-1 levels were observed at earlier ages of B2 (p = 0.003) and M onset (p = 0.041). A taller prepubertal height was observed at younger ages of B2 and M (p=<0.001 and 0.002, respectively). The hazard proportional regression models (HR) showed that with an increase of 1 SD in IGF-1, the HR of presenting B2 at younger ages was 1.25, and this association was maintained when adjusted for confounding variables. Similarly, the HR of presenting M at earlier ages was 1.21. This association was maintained only when adjusting for body mass index but not using further confounders. In boys, prepubertal IGF-1 showed a tendency to be significantly higher in children with earlier G2 and taller height (both p < 0.001). The HR of presenting G2 at younger ages was 1.22, and this association was maintained after adjusting for confounders. CONCLUSIONS: Higher IGF-1 levels in mid-childhood are associated with earlier puberty onset. The role of IGF-1 in the onset of puberty requires further investigation.

Total and Central Adiposity Are Associated With Age at Gonadarche and Incidence of Precocious Gonadarche in Boys.

CONTEXT: A close link between body mass index (BMI) and female pubertal onset is well established. However, observations in boys remain inconclusive. OBJECTIVE: We aim to determine whether BMI as well as total and central adiposity in prepubertal Chilean boys is associated with pubertal timing. METHODS: We performed a longitudinal study in which 494 boys from the Growth and Obesity Chilean Cohort Study were followed starting from birth and throughout puberty, including 5 prepubertal visits. The main outcome measures included anthropometric data and semi-annual clinical pubertal staging. The association between BMI, obesity (BMI standard deviation score [SDS] ≥ 2) and central adiposity (waist circumference ≥ 90th centile) with precocious puberty and age at gonadarche was analyzed using survival- and logistic regression models. RESULTS: BMI, prevalence of total obesity, and central obesity increased throughout childhood. Among the study population, 45 boys entered puberty before the age of 9 years (9.1%). Obesity at 4 to 7 years and childhood mean BMI SDS were significantly associated with precocious gonadarche. Mean age at testicular enlargement (≥4 mL), was 11.0 years (95% CI, 10.9-11.1) and was inversely associated with BMI SDS, waist circumference, and percentage fat mass in almost all prepubertal visits. Age at testicular enlargement in normal weight, overweight, and obese boys was 11.2 (11.0-11.3), 10.9 (10.6-11.1) and 10.7 (10.4-11.1) years, respectively. CONCLUSION: Our observation supports the association of BMI SDS and obesity with pubertal timing and precocious gonadarche in boys, respectively. Early intervention controlling the obesity epidemic could be useful in decreasing detrimental impact on later health.