title: First Pregnancy Characteristics, Postmenopausal Breast Density, and Salivary Sex Hormone Levels in a Population at High Risk for Breast Cancer.
abstract: BACKGROUND
  It remains unknown if later life breast cancer risk as determined by reproductive history is mediated by postmenopausal breast density and/or sex steroid levels.
  
  
  METHODS
  Increased breast density is a strong surrogate for future breast cancer risk. A cross-sectional study with a longitudinal follow up for breast health outcomes evaluated women without breast cancer (n = 1,023; 682 = parous), drawn from a high risk postmenopausal population, with questionnaire reported reproductive histories. The questionnaire was linked to prospective screening mammogram breast density measurements, and saliva biospecimens that were used to assess sex steroid hormone levels.
  
  
  RESULTS
  Expected age and postmenopause related declines in salivary estradiol (E), progesterone (P), dehydroepiandrosterone (DHEA) and testosterone (T) levels were observed. This was most pronounced for DHEA and T, which were also the only postmenopausal hormone levels significantly associated with any reproductive characteristics: parity and breast feeding for DHEA, age-at-first birth for T. Postmenopausal breast density was borderline significantly lower with parity and higher body mass index (BMI). After multivariate analysis, T was the only hormone level to retain any association (negative, p<0.05) with breast density.
  
  
  CONCLUSIONS
  While reproductive characteristics, in particular parity, generally demonstrated independent associations with postmenopausal breast density and E, P and DHEA levels, T levels showed concordant inverse associations with age-at-first birth and breast density. These findings suggest that reproductive effects and later life salivary sex steroid hormone levels may have independent effects on later life breast density and cancer risk.
authors: Kaiser Permanente Department of Surgery, San Rafael, CA.
authors: Mary
authors: M
authors: Mockus
authors: Marin County Department of Health and Human Services, San Rafael, CA.
authors: LeeAnn
authors: L
authors: Prebil
authors: Marin County Department of Health and Human Services, San Rafael, CA.
authors: Rochelle
authors: R
authors: Ereman
authors: Aeron Biotechnology, Hayward, CA.
authors: Charles
authors: C
authors: Dollbaum
authors: Marin County Department of Health and Human Services, San Rafael, CA.
authors: Mark
authors: M
authors: Powell
authors: Buck Institute for Research on Aging, Novato, CA.
authors: Christina
authors: C
authors: Yau
authors: Buck Institute for Research on Aging, Novato, CA.
authors: Christopher C
authors: CC
authors: Benz
keywords: Mammographic Density; Postmenopausal Breast Cancer Risk Cohort; Reproductive History; Saliva Biospecimens; Salivary Sex Steroid Levels