title: Plasma selenium and plasma and erythrocyte glutathione peroxidase activity increase with estrogen during the menstrual cycle.
abstract: OBJECTIVE
  This study was designed to determine the timing and magnitude of changes in selenium status in relation to the fluctuation of 17-beta-estradiol during the menstrual cycle and the effect of different phases of the menstrual cycle on dietary selenium intake.
  
  
  METHODS
  Plasma 17-beta-estradiol and plasma and erythrocyte selenium and glutathione peroxidase (GPx) activity were measured in fasting blood samples collected in the morning at four times over three phases of the menstrual cycle: early follicular (EF: days 1-3 menstruation), periovulatory (PO; E-1: 1 day before estrogen peak and E: during estrogen peak) and mid-luteal (ML: 7-9 days after ovulation) in healthy women (n = 14) aged 21 to 39 years and with regular menstrual cycles (26 to 30 days). The estrogen peak was confirmed by measurement of the luteinizing hormone surge. Dietary records (three-day) coincided with blood collection for each phase.
  
  
  RESULTS
  Plasma selenium and plasma and erythrocyte GPx activity were greatest during the periovulatory phase, coinciding with the estrogen peak. No differences were observed for erythrocyte selenium or dietary selenium throughout the cycle. A linear relationship existed between estradiol and plasma selenium (p < 0.0027), plasma GPx activity (p < 0.0001), and erythrocyte GPx activity (p < 0.0001).
  
  
  CONCLUSIONS
  These results indicate that blood selenium parameters fluctuate during the menstrual cycle such that the phase of the cycle should be considered when assessing selenium status.
authors.affiliation: Department of Human Nutrition, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Eun Jeong
authors.initials: EJ
authors.lastname: Ha
authors.forename: Anne M
authors.initials: AM
authors.lastname: Smith
mesh_terms: D000328:Adult; D004912:Erythrocytes / Q000737:chemistry* / Q000201:enzymology; D004958:Estradiol / Q000097:blood*; D005260:Female; D005979:Glutathione Peroxidase / Q000097:blood / Q000378:metabolism*; D006801:Humans; D008597:Menstrual Cycle / Q000097:blood / Q000502:physiology*; D009752:Nutritional Status; D012643:Selenium / Q000097:blood*
chemical_list: D004958:Estradiol; D005979:Glutathione Peroxidase; D012643:Selenium