Document Type

Capstone Experience

Graduation Date

5-2026

Degree Name

Master of Public Health

Department

Environmental, Agricultural & Occupational Health

First Committee Member

Eleanor Rogan, PhD

Second Committee Member

Laura Tenner, MD, MPH

Third Committee Member

Muhammad Zahid, PhD, MPH

Abstract

The link between estrogen and cancer initiation or progression has been well established; such that the World Health Organization’s International Agency for Research on Cancer (WHO IARC) has classified several estrogen therapies and estrogenic compounds as group 1 carcinogens. Estrogen and/or its receptors have been associated with reproductive cancers such as breast, ovarian, endometrial, and prostate, as well as lymphomas, lung, and colon cancers. Additionally, elevated levels of estrogen and altered gut microbiomes are also associated with increased rates of breast cancer. More recently, microbial genes that are capable of synthesizing estrogen and deconjugating estrogen metabolites have been identified, and evidence supports deconjugating enzymes contributing to estrogen homeostasis. Thus far, much of the data suggesting a role for the gut microbiome in systemic estrogen levels has been correlative. This review summarizes endogenous estrogens in the gastrointestinal tract, estrogen metabolites in feces, and microbial estrogen synthesis or metabolizing enzymes to provide insight into how a shift in microbiome may alter circulating estrogens and affect outcomes in estrogen associated cancers. Finally, knowledge gaps regarding the impact of the microbiome on estrogen metabolism are discussed.

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