Changes in gut bacteria can alter estrogen levels and increase the likelihood of endometrial cancer (EC), according to a review on the relationship between the gut microbiome and sex hormones published recently in the World Journal of Clinical Oncology.
EC, which begins in the lining of the uterus, is a hormone-driven cancer influenced by circulating estrogen levels. When intestinal bacteria that regulate estrogen activity become imbalanced, hormone levels can rise, encouraging the growth of cancer cells in the reproductive tract.
“Whether specific GM [gut microbiome] is causative or curative, discerning the microbiota’s involvement in the different sex-hormone driven cancers is still largely unknown,” explained the authors of this review. They continued, “GM is involved in the estrogen cycle, thus establishing the estrogen-GM axis.”
Estrogens are steroid hormones mainly produced by the ovaries and placenta, though other organs also contribute. They are essential for reproduction and help maintain vaginal health by thickening the epithelium, increasing mucus, and supporting beneficial bacteria. Gut microbes influence how much active estrogen circulates in the body by producing an enzyme called β-glucuronidase. This enzyme converts inactive estrogens into their active forms, allowing them to reenter the bloodstream and attach to estrogen receptors.
Read more about the causes and risk factors for EC
When gut dysbiosis occurs—meaning the microbial community becomes less diverse—β-glucuronidase activity decreases, leading to lower estrogen levels and possible hormonal imbalance. However, an overgrowth of certain β-glucuronidase-producing bacteria can have the opposite effect, boosting circulating estrogens and potentially driving the development of hormone-sensitive cancers such as endometrial, breast, ovarian, and cervical cancers. Studies have identified specific bacterial species, including Porphyromonas and Atopobium vaginae, in patients with EC that appear to promote tissue overgrowth and malignancy.
For patients, these discoveries highlight that the gut is more than a digestive organ as it plays a role in hormone regulation and cancer risk. Maintaining microbial balance through diet may be one practical step. Diets rich in fiber and plant compounds called phytoestrogens, found in foods such as soy and flaxseed, can help modulate estrogen levels. Conversely, high-fat diets and certain antibiotics may disrupt the microbiome, leading to unfavorable hormonal effects.
Probiotics, prebiotics, and possibly newer “postbiotic” treatments are being studied as ways to restore gut balance and regulate estrogen metabolism safely. While more research is needed, patients can already benefit from understanding how gut health connects to reproductive health. By nurturing a diverse microbiome, it may be possible to help prevent or slow the progression of estrogen-related cancers such as EC.
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