Bacteria in Your Colon Reactivate Sex Hormones to Control Gut Movement

Researchers at Boston Children's Hospital and Harvard Medical School have uncovered what may be an entirely new signaling axis between gut bacteria, sex hormones, and the neurons that keep your intestines moving. The finding, published in Nature Neuroscience on June 2, 2026, suggests that a specific bacterial enzyme converts inactive androgen hormones into active forms, which then instruct nerve cells in the colon wall to regulate transit. If the mechanism holds up in humans, it could fundamentally change how clinicians think about conditions like irritable bowel syndrome, and about the digestive side effects of antibiotics.

Gut bacteria convert inactive androgens into colon-control signals

Androgens are steroid hormones, testosterone being the most familiar, that the body typically associates with reproductive and developmental functions. What this study proposes is that gut microbes play a previously unknown role in maintaining those hormones' activity where it matters for digestion. The liver conjugates androgens with glucuronic acid and excretes them into the gut in an inactive form called androgen-glucuronides. Specific gut bacteria, equipped with an enzyme called beta-glucuronidase (GUS), then strip away that glucuronic acid, regenerating active androgens on-site in the colon.

Those reactivated hormones bind to androgen receptors on two types of neurons: Nos1-positive enteric neurons embedded in the gut wall, and Scn10a-positive spinal afferent neurons. In male mice, 95% of androgen receptor-positive enteric neurons were inhibitory motor neurons marked by NOS1. The researchers found that androgen signaling to these cells is required for normal intestinal transit. When microbial populations were wiped out with antibiotics, androgen receptor expression in enteric neurons vanished, serum testosterone dropped, and gut motility broke down. Delivering the bacterial GUS enzyme directly into the colon of antibiotic-treated mice restored androgen signaling and partly rescued the motility defect.

This is a meaningful extension of what scientists already know about how gut microbiota regulate GI motility through hormonal and neural channels, but the specific androgen-reactivation loop had not been described before.

Why IBS patients and antibiotic users may be most affected

Millions of people develop IBS or similar gut disorders following a gastrointestinal infection or a course of antibiotics, a phenomenon clinicians call post-infectious IBS or antibiotic-associated dysmotility. The new research offers a plausible biological mechanism for why that happens. If broad-spectrum antibiotics eliminate the bacteria that reactivate gut androgens, the nerve cells governing colon movement lose a critical hormonal signal, and transit slows or becomes erratic.

"Our findings imply that short courses of broad-spectrum antibiotics that are routinely used in clinical and veterinary medicine may be disrupting not only nerve function but also sex hormone signaling throughout the body," said Meenakshi Rao, the study's lead researcher.

The gut conditions this research speaks to are not trivial in scope. IBS already impacts quality of life and work productivity for a large share of the global population, and existing treatments address symptoms rather than underlying biology. A mechanism rooted in microbial enzyme activity is, at least in principle, targetable: you could imagine delivering GUS enzyme locally or protecting GUS-producing bacteria from antibiotic collateral damage.

Antibiotic experiments and genetically engineered mice isolated the mechanism

The team's experimental design combined several complementary approaches to pin down causality rather than correlation. Gut microorganisms in mice were dramatically reduced using antibiotics, and researchers then monitored intestinal transit while measuring androgen levels. Immunohistochemistry identified which neurons in the gut wall carried androgen receptors and which did not. Genetically engineered mice were built so that specific cell populations could not respond to testosterone at all, allowing the researchers to confirm that androgen signaling in those neurons was the relevant variable, not some bystander effect.

The bacterial enzyme identification step drew on methods similar to those used in gnotobiotic mouse studies, where researchers introduce known microbial components to animals with depleted microbiomes to test specific functional hypotheses. Delivering isolated GUS enzyme into antibiotic-treated mice provided the cleanest evidence: restore the enzyme, restore the signal, partially restore function.

Nos1 neurons also showed a developmentally interesting pattern: androgen receptor expression ramped up at puberty, correlated with shifts in fecal bacterial beta-glucuronidase activity. That timing correlation suggests the microbiome and the host nervous system may co-develop in ways that have not been fully mapped.

Open questions about female biology and other microbial metabolites

The study's current findings are largely limited to male mice. Androgen signaling had minimal effects on gut motility in female mice, which had fewer androgen receptor-positive enteric neurons. That difference is biologically interesting but means the female side of this story remains largely unwritten. Whether estrogen or other sex hormones interact with gut bacteria through analogous enzyme-driven loops is an open question the current data cannot answer.

The translational gap from mouse studies to human clinical outcomes is also real. Microbiome research in general has struggled to convert compelling mouse findings into reproducible clinical results, and this mechanism will need human validation before any therapeutic applications are pursued. Additionally, androgens are one of many microbial metabolites that influence GI motility; the microbiome regulates gut hormone secretion through serotonin, GLP peptides, and peptide YY as well, and how much the androgen pathway contributes relative to those signals in humans is not yet clear.

What the team plans to pursue next in gut-nerve research

The Boston Children's Hospital team intends to keep pulling on this thread, focusing on how gut microorganisms interact with the nervous system more broadly to shape digestive health. "The colon is an organ in which a lot of different systems in the body converge, including hormones, bacteria, immune cells and nerves," Rao said, and this work adds a specific enzymatic mechanism to that intersection. The GUS enzyme is a plausible therapeutic target: it is microbially produced, locally acting, and appears sufficient to at least partly restore normal signaling when delivered directly. Whether that translates into a probiotic approach, a microbiome-sparing antibiotic strategy, or something else will depend on what human studies show.

For now, the study adds a concrete reason to treat antibiotic prescriptions as a decision with digestive consequences that go beyond killing pathogens. Protecting the bacteria that keep your hormones active in your colon may matter more than anyone previously realized.

Evidence rating

INVESTIGATIONAL — 75/100

Caveats:

• All experiments were conducted in mice; human validation has not yet been performed.
• The effect was pronounced in male mice; female mice showed minimal androgen receptor expression in enteric neurons, so applicability across sexes is uncertain.
• Funding source was not disclosed in the available reporting; independent replication has not yet been published.
• Other microbial metabolites also influence gut motility, and the relative importance of androgen reactivation among these pathways remains unknown.

This is a preclinical mechanistic study conducted entirely in mice. It identifies a specific causal chain — bacterial GUS enzymes → active androgens → enteric neuron signaling → gut motility — with named molecular players and rescue experiments, but no human data have been reported. Results cannot yet be generalized to humans, and independent replication has not been published.

References

1. Valentina N. Lagomarsino, Ariel Robinson, Perry E. Mitchell, et al. (2026). Microbial reactivation of host androgens directs enteric neuronal regulation of gut motility. Nature Neuroscience. https://doi.org/10.1038/s41593-026-02321-0
2. Zhipeng Zheng, Jingyi Tang, Yingnan Hu, Wei Zhang (2022). Role of gut microbiota-derived signals in the regulation of gastrointestinal motility. Frontiers in Medicine. https://doi.org/10.3389/fmed.2022.961703
3. Xinyu Cheng, Cheng Ren, Xiaofei Mei, Yufeng Jiang, Yafeng Zhou (2024). Gut microbiota and irritable bowel syndrome: status and prospect. Frontiers in Medicine. https://doi.org/10.3389/fmed.2024.1429133
4. M. Grover, P. C. Kashyap (2014). Germ‐free mice as a model to study effect of gut microbiota on host physiology. Neurogastroenterology & Motility. https://doi.org/10.1111/nmo.12366
5. Raul de Jesus Cano, Gissel García Menéndez (2026). Why Clinical Trials of Microbiome-Targeted Interventions Often Fail to Support Health Claims: A Commentary on Probiotics and Translational Design. Microorganisms. https://doi.org/10.3390/microorganisms14020470
6. Jessica Chao, Rosemary A Coleman, Damien J Keating, Alyce M Martin (2025). Gut Microbiome Regulation of Gut Hormone Secretion. Endocrinology. https://doi.org/10.1210/endocr/bqaf004