title: Plasma concentrations of beta-endorphin in trained eumenorrheic and amenorrheic women.
abstract: OBJECTIVE
  To characterize the pattern of plasma beta-endorphin throughout the normal menstrual cycle and test the hypothesis that beta-endorphin concentrations are elevated in trained women with amenorrhea compared with trained and sedentary eumenorrheic women.
  
  
  METHODS
  Cohort analytic study.
  
  
  METHODS
  Academic research environment.
  
  
  METHODS
  Healthy female volunteers: 10 eumenorrheic sedentary, 11 eumenorrheic trained, and 11 amenorrheic trained women.
  
  
  METHODS
  Blood samples were collected three times per week for either one complete menstrual cycle (eumenorrheic sedentary and trained subjects) or for a 4-week period (amenorrheic trained subjects).
  
  
  METHODS
  Plasma beta-endorphin concentrations.
  
  
  RESULTS
  beta-Endorphin levels varied considerably across the sampling period and were not associated with menstrual status, gonadotropin, or gonadal steroid concentrations. Average beta-endorphin levels were not different between the follicular and luteal phases for menstruating subjects, but were greater in the eumenorrheic athletes. Compared with eumenorrheic sedentary subjects, plasma beta-endorphin levels were higher in the athletic groups, regardless of menstrual status.
  
  
  CONCLUSIONS
  There were no cycle-related beta-endorphin changes. Eumenorrheic and amenorrheic athletes have higher beta-endorphin concentrations that may reflect adaptations to intense training and not exercise-associated amenorrhea.
authors.affiliation: Department of Reproductive Biology, McMaster University, Hamilton, Ontario, Canada. vharber@per.ualberta.ca
authors.forename: V J
authors.initials: VJ
authors.lastname: Harber
authors.forename: J R
authors.initials: JR
authors.lastname: Sutton
authors.forename: J D
authors.initials: JD
authors.lastname: MacDougall
authors.forename: C A
authors.initials: CA
authors.lastname: Woolever
authors.forename: B R
authors.initials: BR
authors.lastname: Bhavnani
mesh_terms: D000328:Adult; D000568:Amenorrhea / Q000097:blood*; D015331:Cohort Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D012739:Gonadal Steroid Hormones / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008597:Menstrual Cycle / Q000097:blood*; D011388:Prolactin / Q000097:blood; D012146:Rest / Q000502:physiology; D001615:beta-Endorphin / Q000097:blood*
chemical_list: D012739:Gonadal Steroid Hormones; D006065:Gonadotropins, Pituitary; D001615:beta-Endorphin; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone