title: Association of Obesity with Onset of Puberty and Sex Hormones in Chinese Girls: A 4-Year Longitudinal Study.
abstract: OBJECTIVE
  To examine the influence of childhood obesity on the early onset of puberty and sex hormones in girls.
  
  
  METHODS
  Healthy girls with different percentages of body fat at baseline (40 obese, 40 normal, and 40 lean) were recruited from three elementary schools in Shenyang, China. These girls (mean age 8.5 years) were also matched by height, school grade, Tanner stage, and family economic status at baseline. Anthropometry, puberty characteristics, and sex hormone concentrations were measured at baseline and at each follow-up visit. The generalized estimating equation model and analysis of variance for repeated measures using a generalized linear model were used to determine the differences in puberty characteristics and sex hormones among three groups.
  
  
  RESULTS
  Over 4 years, mean age of breast II onset was earlier among obese girls (8.8 years) than normal girls (9.2 years) and lean girls (9.3 years). The prevalence (%) of early-maturation in the obese, normal, and lean groups was 25.9%, 11.1%, and 7.4%, respectively. Obesity was associated with an increased risk for breast stage II (year 2: RR, 6.3; 95% CI, 1.9-21.1 and year 3: RR, 6.9; 95% CI, 0.8-60.1). None of the girls experienced menarche in the first year; however, by the fourth year 50.0% of obese girls had menarche onset, which was higher than normal weight (27.5%) and lean girls (8.1%). The mean estradiol level increased with age in the obese, normal, and lean groups. The mean estradiol concentration was higher in obese girls than in normal and lean girls throughout the 4-year period (P<0.05).
  
  
  CONCLUSIONS
  Childhood obesity contributes to early onset of puberty and elevated levels of estradiol in girls.
authors.affiliation: Department of Maternal and Child Health, School of Public Health, China Medical University, Shenyang, Liaoning Province, China, 110013.
authors.forename: Lingling
authors.initials: L
authors.lastname: Zhai
authors.affiliation: Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, United States of America 29208.
authors.forename: Jihong
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Pharmacology, Shenyang Pharmaceutical University, Shenyang, Liaoning Province, China, 110016.
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Epidemiology and Biostatistics, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina, United States of America 29208.
authors.forename: Junxiu
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Maternal and Child Health, School of Public Health, China Medical University, Shenyang, Liaoning Province, China, 110013.
authors.forename: Yinglong
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Department of Maternal and Child Health, School of Public Health, China Medical University, Shenyang, Liaoning Province, China, 110013.
authors.forename: Lihong
authors.initials: L
authors.lastname: Jia
authors.affiliation: Department of Maternal and Child Health, School of Public Health, China Medical University, Shenyang, Liaoning Province, China, 110013.
authors.forename: Xingjia
authors.initials: X
authors.lastname: Yao
mesh_terms: D044466:Asian People; D001940:Breast / Q000254:growth & development; D002648:Child; D002681:China; D004958:Estradiol / Q000032:analysis*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007118:Immunoassay; D016014:Linear Models; D008137:Longitudinal Studies; D063766:Pediatric Obesity / Q000175:diagnosis*; D015995:Prevalence; D011627:Puberty; D011863:Radioimmunoassay; D012306:Risk; D012463:Saliva / Q000378:metabolism; D012741:Sexual Maturation; D013739:Testosterone / Q000032:analysis
chemical_list: D013739:Testosterone; D004958:Estradiol