title: Application of the estrogen threshold hypothesis to the physiologic hypoestrogenemia of lactation.
abstract: OBJECTIVE
  This study determined the impact of breastfeeding on hypoestrogenic symptoms among women in the postpartum period and correlated these findings with the Estrogen Threshold Hypothesis, which postulates that the hypoestrogenic symptoms experienced are related to circulating estrogen levels.
  
  
  METHODS
  Using a survey instrument that combined previously validated assessments of postpartum mood changes and menopausal symptoms, women were evaluated in the immediate postpartum period, prior to hospital discharge, and at 3 and 6 weeks postpartum. Each time period was analyzed independently, in a cross-sectional design, where women were categorized as "breastfeeding" or "bottle feeding."
  
  
  RESULTS
  Of 236 women recruited, 171 (72.5%) intended to breastfeed, and 62 (26.3%) intended to bottle feed. At both the 3- and 6-week postpartum evaluations, a similar percentage of women in the breastfeeding and bottle-feeding groups reported hot flashes. However, breastfeeding women were more likely to report vaginal dryness than those who did not breastfeed: 20/150 (13.3%) versus 3/80 (3.8%) at 3 weeks, p<0.05; 25/143 (17.5%) versus 2/87 (2.3%) at 6 weeks, p<0.001.
  
  
  CONCLUSIONS
  The Estrogen Threshold Hypothesis accurately predicts the findings of increased reported vaginal dryness but not hot flashes during lactation.
authors.affiliation: 1 Department of Reproductive Medicine, School of Medicine, University of California , San Diego, La Jolla, California.
authors.forename: Sanjay K
authors.initials: SK
authors.lastname: Agarwal
authors.forename: Julie
authors.initials: J
authors.lastname: Kim
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Korst
authors.forename: Claude L
authors.initials: CL
authors.lastname: Hughes
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000097:blood; D001903:Bottle Feeding; D001942:Breast Feeding; D003430:Cross-Sectional Studies; D004967:Estrogens / Q000097:blood*; D005260:Female; D019584:Hot Flashes / Q000097:blood*; D006801:Humans; D007231:Infant, Newborn; D007774:Lactation / Q000097:blood / Q000502:physiology*; D049590:Postpartum Period; D011237:Predictive Value of Tests; D014621:Vagina / Q000473:pathology*; D014623:Vaginal Diseases / Q000209:etiology / Q000473:pathology*
chemical_list: D015415:Biomarkers; D004967:Estrogens