PurposePuberty onset exhibits remarkable inter-individual and ethnic differences. 5% of Chileans are indigenous but puberty ethnic disparities have not been studied. We aim for evaluating precocious puberty prevalence in children with Mapuche ancestry vs non-indigenous Chilean children (according to their surnames).MethodsLongitudinal cohort study: 1003 children (50.2% girls) participating in the Growth and Obesity Chilean Cohort Study (GOCS) were studied. Annual anthropometry was measured since 4-7years. Subsequently, Tanner staging and anthropometry were measured every 6months. In girls, Tanner stage was assessed by breast palpation and in boys by testicular volume measurements. The cohort was stratified in three groups depending on Mapuche surname numbers as follows: (A) no indigenous surnames (n=811), (B) one to two indigenous surnames (n=147), and (C) three or more indigenous surnames (n=45). We evaluated the prevalence of precocious thelarche, pubarche, menarche and gonadarche (testicular volume4mlG2), using a cutoff age of 8years in girls and 9years in boys while controlling for socioeconomic status, body mass index, waist circumference, IGF-1 and DHEAS at 7years.ResultsIn girls, no significant differences were observed. On the contrary, in boys, precocious gonadarche prevalence was higher in group C (29.2%) vs group A (6.0%) and vs group B (10.5%) (p=0.001, p=0.004, respectively). Increased precocious gonadarche and pubarche risks in group C were observed even after adjustment [OR 7.31; 95% IC (2.32-23.51); p=0.001] and [OR 6.17, 95% CI (1.62-23.49); p=0.008], respectively.ConclusionIndigenous origin in Chile is an independent risk factor for precocious gonadarche and pubarche in boys but not in girls.