Computational and Mathematical Methods in Medicine
Volume 2012 (2012), Article ID 792375, 8 pages
Research Article

An Estrogen Model: The Relationship between Body Mass Index, Menopausal Status, Estrogen Replacement Therapy, and Breast Cancer Risk

1Dominican University of California, 50 Acacia Avenue, San Rafael, CA 94901, USA
2Archimedes, Inc., 201 Mission Street, San Francisco, CA 94105, USA
3American Cancer Society, 250 Williams Street NW, Atlanta, GA 30303, USA

Received 5 August 2011; Accepted 3 October 2011

Academic Editor: Niko Beerenwinkel

Copyright © 2012 Linda E. Green et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We present a mathematical model that lends support to the hypothesis that estrogen levels mediate the complex relationship between body mass index (BMI), menopausal status, estrogen-only hormone replacement therapy (HRT), and breast cancer risk. The model predicts a decrease in the relative risk of breast cancer of 3% per unit increase in BMI (kg/m2) for premenopausal women and an increase in the relative risk of 4% per unit increase in BMI for postmenopausal women who are not HRT users. When comparing postmenopausal women who use estrogen-only HRT to postmenopausal women who do not use HRT, the model predicts an increased risk of breast cancer associated with use of estrogen that diminishes with increasing BMI, with a relative risk of 1.6 for women with BMI of 18, 1.2 for women with BMI of 25, and 1.0 for women with B M I 3 0 . Model predictions agree with data from five major epidemiological studies.