title: Comparison of postmenopausal endogenous sex hormones among Japanese, Japanese Brazilians, and non-Japanese Brazilians.
abstract: BACKGROUND
  Differences in sex hormone levels among populations might contribute to the variation in breast cancer incidence across countries. Previous studies have shown higher breast cancer incidence and mortality among Japanese Brazilians than among Japanese. To clarify the difference in hormone levels among populations, we compared postmenopausal endogenous sex hormone levels among Japanese living in Japan, Japanese Brazilians living in the state of São Paulo, and non-Japanese Brazilians living in the state of São Paulo.
  
  
  METHODS
  A cross-sectional study was conducted using a control group of case-control studies in Nagano, Japan, and São Paulo, Brazil. Participants were postmenopausal women older than 55 years of age who provided blood samples. We measured estradiol, estrone, androstenedione, dehydroepiandrosterone sulfate (DHEAS), testosterone and free testosterone by radioimmunoassay; bioavailable estradiol by the ammonium sulfate precipitation method; and sex hormone-binding globulin (SHBG) by immunoradiometric assay. A total of 363 women were included for the present analyses, comprising 185 Japanese, 44 Japanese Brazilians and 134 non-Japanese Brazilians.
  
  
  RESULTS
  Japanese Brazilians had significantly higher levels of estradiol, bioavailable estradiol, estrone, testosterone and free testosterone levels, and lower SHBG levels, than Japanese. Japanese Brazilians also had significantly higher levels of bioavailable estradiol, estrone and DHEAS and lower levels of SHBG and androstenedione than non-Japanese Brazilians. Levels of estradiol, testosterone and free testosterone, however, did not differ between Japanese Brazilians and non-Japanese Brazilians. These differences were observed even after adjustment for known breast cancer risk factors. We also found an increase in estrogen and androgen levels with increasing body mass index, but no association for most of the other known risk factors.
  
  
  CONCLUSIONS
  We found higher levels of estrogens and androgens in Japanese Brazilians than in Japanese and levels similar to or higher than in non-Japanese Brazilians. Our findings may help explain the increase in the incidence and mortality rate of breast cancer among Japanese Brazilians.
authors.affiliation: Epidemiology and Prevention Division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan. moiwasak@ncc.go.jp
authors.forename: Motoki
authors.initials: M
authors.lastname: Iwasaki
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kasuga
authors.forename: Shiro
authors.initials: S
authors.lastname: Yokoyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Onuma
authors.forename: Hideki
authors.initials: H
authors.lastname: Nishimura
authors.forename: Ritsu
authors.initials: R
authors.lastname: Kusama
authors.forename: Gerson Shigeaki
authors.initials: GS
authors.lastname: Hamada
authors.forename: Ines Nobuko
authors.initials: IN
authors.lastname: Nishimoto
authors.forename: Maria do Socorro
authors.initials: Mdo S
authors.lastname: Maciel
authors.forename: Juvenal
authors.initials: J
authors.lastname: Motola
authors.forename: Fábio Martins
authors.initials: FM
authors.lastname: Laginha
authors.forename: Roberto
authors.initials: R
authors.lastname: Anzai
authors.forename: Shoichiro
authors.initials: S
authors.lastname: Tsugane
mesh_terms: D000328:Adult; D000368:Aged; D000645:Ammonium Sulfate / Q000737:chemistry; D044466:Asian People; D001938:Brazil; D005591:Chemical Fractionation; D003430:Cross-Sectional Studies; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006801:Humans; D007564:Japan; D008875:Middle Aged; D017698:Postmenopause / Q000502:physiology*; D011863:Radioimmunoassay
chemical_list: D012739:Gonadal Steroid Hormones; D000645:Ammonium Sulfate