The Effects of Physical Exercise on Selected Markers of Estrogen Metabolism Linked to Breast Cancer Risk in Premenopausal Women

Background: Physical activity is linked to breast cancer risk reduction in women, yet the mechanism remains largely unknown. Possible causes for this association have been hypothesized to include change in endogenous estrogen production, estrogen metabolism, circulating concentrations of peptide hormones and growth factors, obesity, central adiposity, and immune function. Recent investigations in estrogen metabolism in women have brought to light a new possibility for the association between physical activity and breast cancer risk to be related to 2-hydroxyestrone metabolism increases with exercise, relative to 16αhydroxyestrone. This metabolite pathway has been studied as a mechanism for postmenopausal breast cancer risk, but there are few studies concerning eumenorrheic, premenopausal women. The purpose of this systematic review is to evaluate the most current research on this topic. Methods: An exhaustive search of available medical literature concerning estrogen metabolism, breast cancer risk, physical activity, and premenopausal females was conducted. The reviewed studies were limited to randomized controlled trials, and prospective and retrospective cohort investigations. Results: The six articles included in this review showed either non-significant changes in estrogen metabolism to favor the anti-estrogenic 2-hydroxyestrone pathway, or no change at all in estrogen metabolism as a result of physical activity. The only investigation reaching statistically significant results was a retrospective cohort study relying on self-reports of physical activity. The six studies reviewed demonstrate vastly different inclusion and exclusion criteria, as well as intervention protocols, causing comparison between studies to be imprecise. Conclusion: Current research has yet to identify the cause of the association between physical activity and reduced breast cancer risk as related to changes in estrogen metabolism. Further investigation with large randomized controlled trials with objectively measuring physical activity, utilizing standardized methods of gathering and analyzing data is needed. Degree Type Capstone Project Rights Terms of use for work posted in CommonKnowledge. This capstone project is available at CommonKnowledge: http://commons.pacificu.edu/pa/219 Copyright and terms of use If you have downloaded this document directly from the web or from CommonKnowledge, see the “Rights” section on the previous page for the terms of use. If you have received this document through an interlibrary loan/document delivery service, the following terms of use apply: Copyright in this work is held by the author(s). You may download or print any portion of this document for personal use only, or for any use that is allowed by fair use (Title 17, §107 U.S.C.). Except for personal or fair use, you or your borrowing library may not reproduce, remix, republish, post, transmit, or distribute this document, or any portion thereof, without the permission of the copyright owner. [Note: If this document is licensed under a Creative Commons license (see “Rights” on the previous page) which allows broader usage rights, your use is governed by the terms of that license. ] Inquiries regarding further use of these materials should be addressed to: CommonKnowledge Rights, Pacific University Library, 2043 College Way, Forest Grove, OR 97116, (503) 352-7209. Email inquiries may be directed to:. copyright@pacificu.edu This capstone project is available at CommonKnowledge: http://commons.pacificu.edu/pa/219 NOTICE TO READERS This work is not a peer-reviewed publication. The Master’s Candidate author of this work has made every effort to provide accurate information and to rely on authoritative sources in the completion of this work. However, neither the author nor the faculty advisor(s) warrants the completeness, accuracy or usefulness of the information provided in this work. This work should not be considered authoritative or comprehensive in and of itself and the author and advisor(s) disclaim all responsibility for the results obtained from use of the information contained in this work. Knowledge and practice change constantly, and readers are advised to confirm the information found in this work with other more current and/or comprehensive sources. The student author attests that this work is completely his/her original authorship and that no material in this work has been plagiarized, fabricated or incorrectly attributed.