title: Longitudinal study of insulin resistance and sex hormones over the menstrual cycle: the BioCycle Study.
abstract: BACKGROUND
  Conflicting findings have been reported regarding the effect of menstrual cycle phase and sex hormones on insulin sensitivity.
  
  
  OBJECTIVE
  The aim was to determine the pattern of insulin resistance over the menstrual cycle and whether variations in sex hormones explain these patterns.
  
  
  METHODS
  The BioCycle study is a longitudinal study that measured hormones at different phases of the menstrual cycle. Participants had up to eight visits per cycle; each visit was timed using fertility monitors to capture sensitive windows of hormonal changes.
  
  
  METHODS
  The study was conducted in the general community of the University at Buffalo (Buffalo, NY).
  
  
  METHODS
  A total of 257 healthy, premenopausal women (age, 27±8 yr; body mass index, 24±4 kg/m2) participated in the study.
  
  
  METHODS
  We measured fasting insulin, glucose, and insulin resistance by the homeostasis model of insulin resistance (HOMA-IR).
  
  
  RESULTS
  Significant changes in HOMA-IR were observed over the menstrual cycle; from a midfollicular phase level of 1.35, levels rose to 1.59 during the early luteal phase and decreased to 1.55 in the late-luteal phase. HOMA-IR levels primarily reflected changes in insulin and not glucose. After adjustment for age, race, cycle, and other sex hormones, HOMA-IR was positively associated with estradiol (β=0.082; P<0.001) and progesterone (β=0.025; P<0.001), and inversely associated with FSH (adjusted β=-0.040; P<0.001) and SHBG (β=-0.085; P<0.001). LH was not associated with HOMA-IR. Further adjustment for BMI weakened the association with SHBG (β=-0.057; P=0.06) but did not affect other associations.
  
  
  CONCLUSIONS
  Insulin exhibited minor menstrual cycle variability. Estradiol and progesterone were positively associated with insulin resistance and should be considered in studies of insulin resistance among premenopausal women.
authors.affiliation: Eunice Kennedy Shriver National Institute of Child Health and Human Development, Division of Epidemiology, Statistics, and Prevention Research, Epidemiology Branch, 6100 Executive Boulevard, Room 7B03, MSC 7510, Bethesda, Maryland 20892, USA.
authors.forename: Edwina H
authors.initials: EH
authors.lastname: Yeung
authors.forename: Cuilin
authors.initials: C
authors.lastname: Zhang
authors.forename: Sunni L
authors.initials: SL
authors.lastname: Mumford
authors.forename: Aijun
authors.initials: A
authors.lastname: Ye
authors.forename: Maurizio
authors.initials: M
authors.lastname: Trevisan
authors.forename: Liwei
authors.initials: L
authors.lastname: Chen
authors.forename: Richard W
authors.initials: RW
authors.lastname: Browne
authors.forename: Jean
authors.initials: J
authors.lastname: Wactawski-Wende
authors.forename: Enrique F
authors.initials: EF
authors.lastname: Schisterman
mesh_terms: D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D015992:Body Mass Index; D004522:Educational Status; D005260:Female; D005298:Fertility / Q000502:physiology; D005498:Follicular Phase / Q000502:physiology; D006801:Humans; D007182:Income; D007328:Insulin / Q000097:blood*; D007333:Insulin Resistance / Q000502:physiology*; D008137:Longitudinal Studies; D008183:Luteal Phase / Q000502:physiology; D008597:Menstrual Cycle / Q000502:physiology*; D008598:Menstruation / Q000502:physiology; D018579:Patient Selection; D017697:Premenopause / Q000502:physiology; D044469:Racial Groups; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D007328:Insulin