Purpose: Puberty 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).
Methods: Longitudinal cohort study: 1003 children (50.2% girls) participating in the Growth and Obesity Chilean Cohort Study (GOCS) were studied. Annual anthropometry was measured since 4-7 years. Subsequently, Tanner staging and anthropometry were measured every 6 months. 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 volume ≥ 4 ml-G2), using a cutoff age of 8 years in girls and 9 years in boys while controlling for socioeconomic status, body mass index, waist circumference, IGF-1 and DHEAS at 7 years.
Results: In 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.
Conclusion: Indigenous origin in Chile is an independent risk factor for precocious gonadarche and pubarche in boys but not in girls.
Keywords: Ethnic groups; Indians; Precocious; Puberty; South American.