Estrogen Exposure across the Transition to Menopause

Kathleen A. O'Connor, University of Washington
Eleanor Brindle, University of Washington
Rebecca J. Ferrell, Georgetown University
Jane Shofer, University of Washington
Darryl J. Holman, University of Washington
Rebecca Miller, Drexel University
Deborah E. Schechter, University of Washington
Phyllis Kernoff Mansfield, Pennsylvania State University
James W. Wood, Pennsylvania State University
Maxine Weinstein, Georgetown University

The risk of morbidity and mortality from reproductive-related cancers increases post-menopausally, and risk for some reproductive cancers is associated with lifetime exposure to estrogen. We hypothesize that estrogen exposure during the peri-menopause may be a key factor influencing post-menopausal cancer risk. In a study of reproductive aging we examine total and unopposed estrogen levels across the peri-menopause, and compare them to pre-menopausal (before the peri-menopause) and post-menopausal levels. U.S. participants (n=156, 25-58 years) collected daily urines for 6 months in each of 5 consecutive years. Exposure to total and unopposed estrogen was estimated using urinary estrogen (E) and progesterone (P). The ratio of E to P and the mitotic estrogen threshold are used as indicators of unopposed estrogen, and area under the curve is used as an indicator of total estrogen exposure. Linear mixed effects models are used to test the hypothesis that estrogen exposure, particularly unopposed estrogen, is elevated during the menopausal transition.