Do Probiotics Change Hormones? Understanding the Gut-Endocrine Connection

December 11, 2025 •

5 min read

Emerging research indicates a bidirectional communication pathway between the gut microbiome and the endocrine system, with gut bacteria influencing key hormonal processes. So, do probiotics change hormones directly, or is their impact more subtle, mediated by their effects on gut health and overall metabolic function?

Quick Summary

Probiotics can indirectly modulate various hormone levels by influencing gut microbiome activity, inflammation, and metabolic pathways. Their impact varies depending on the specific hormone, bacterial strain, and the individual's overall health.

Key Points

Indirect Modulation: Probiotics do not produce hormones but influence them indirectly through their effects on gut function, inflammation, and metabolic pathways.
Estrogen and the Estrobolome: Specific gut bacteria in the estrobolome metabolize and regulate circulating estrogen levels, which can be modulated by probiotic intake.
Testosterone Balance: Probiotics have been linked to maintaining youthful testosterone levels in male animals and reducing elevated testosterone in women with conditions like PCOS.
Reduced Cortisol Levels: Research shows certain probiotic strains can help lower stress-induced cortisol levels by influencing the gut-brain axis and reducing inflammation.
Improved Insulin Sensitivity: In conditions like PCOS, probiotics, especially when combined with prebiotics, can improve insulin sensitivity and other metabolic markers by enhancing gut barrier function and producing beneficial SCFAs.
Hormone-Specific Effects: The impact on hormones is highly specific to the probiotic strain and individual, with potential effects noted for estrogen, testosterone, cortisol, insulin, and thyroid hormones.
Supportive Therapy: Probiotics show promise as a supportive therapy for hormonal and metabolic issues, but larger, standardized human trials are needed for definitive clinical guidelines.

The Gut-Endocrine Axis: A Complex Relationship

The human gut is home to trillions of microorganisms collectively known as the gut microbiome. This intricate ecosystem plays a crucial role far beyond digestion, actively participating in communication with the body's hormonal system—a relationship known as the gut-endocrine axis. Hormones can influence the composition of the gut microbiota, and in turn, the gut microbiota can alter the metabolism and regulation of hormones like estrogen, testosterone, cortisol, and insulin. Probiotics, or live beneficial microbes, represent one way to intentionally modulate this delicate balance, though their effects are highly specific and dependent on the individual's health status and the probiotic strain used.

How Probiotics Influence Hormone Metabolism

Probiotics do not produce human hormones directly. Instead, their influence is exerted through several key mechanisms related to gut function and metabolic signaling:

The Estrobolome: This is the collection of gut bacteria that metabolize estrogens, a group of hormones vital for reproductive and overall health. The estrobolome produces an enzyme called beta-glucuronidase, which deconjugates (un-tags) estrogen, allowing it to be reabsorbed into the bloodstream instead of being excreted. A balanced estrobolome helps maintain stable estrogen levels, while an imbalance can lead to fluctuations linked to conditions like premenstrual syndrome (PMS) or menopause symptoms.
Androgen Metabolism: The gut microbiome is also a major regulator of androgen metabolism, which includes testosterone. Some studies suggest that specific probiotic strains, like Lactobacillus reuteri, may help sustain testosterone levels, particularly in aging individuals. In women with conditions like polycystic ovary syndrome (PCOS), probiotics have been shown to help decrease total testosterone and increase sex hormone-binding globulin (SHBG), thereby improving the hormonal profile.
Reduction of Inflammation: Chronic, low-grade inflammation is a known disruptor of hormonal balance and is often linked to conditions like insulin resistance in PCOS. Probiotics can reduce systemic inflammation by strengthening the intestinal barrier, decreasing the translocation of lipopolysaccharides (LPS) from the gut into the bloodstream, and producing anti-inflammatory short-chain fatty acids (SCFAs). This anti-inflammatory action can have a normalizing effect on hormone production and signaling.
Impact on the HPA Axis: The gut-brain axis is a two-way communication system linking the central nervous system, endocrine system, and gut. Probiotics, often called "psychobiotics," can influence the hypothalamic-pituitary-adrenal (HPA) axis, which governs the body's stress response and cortisol production. By producing neurotransmitters like serotonin and GABA, or by activating the vagus nerve, certain probiotic strains have been shown to lower elevated cortisol levels associated with chronic stress.

Probiotic Effects on Key Hormones

The effect of probiotics varies considerably depending on the target hormone and individual health. Some of the most studied hormonal connections include:

Estrogen: As mentioned with the estrobolome, probiotics with beta-glucuronidase activity can affect circulating estrogen levels. Observational studies have noted that probiotic intake is associated with higher estradiol levels in premenopausal women and lower testosterone in postmenopausal women.
Testosterone: In males, some probiotic strains like L. reuteri have been linked to maintaining youthful testosterone levels in animal models, while in women with hyperandrogenism (e.g., PCOS), specific strains like Lactobacillus and Bifidobacterium have been shown to reduce testosterone levels.
Cortisol: Meta-analyses of clinical trials have provided low to moderate evidence that probiotics can reduce cortisol levels, particularly in healthy individuals under stress. This effect is mediated by their influence on the gut-brain-HPA axis.
Insulin: Probiotics, and particularly synbiotics (probiotics plus prebiotics), have demonstrated the ability to improve insulin sensitivity and markers of insulin resistance in individuals with conditions like PCOS or metabolic syndrome. They achieve this by improving the gut barrier, reducing inflammation, and increasing SCFA production.
Thyroid Hormones: The existence of a gut-thyroid axis is recognized, with emerging meta-analyses suggesting that probiotics and synbiotics may beneficially modulate thyroid function. Some studies have noted a significant reduction in thyroid-stimulating hormone (TSH) and an increase in free T3 and T4 levels, particularly in individuals with existing thyroid disorders. However, the evidence is still inconsistent, and more research is needed.

Comparing Probiotic Effects on Different Hormones


Hormone	Probiotic Mechanism	Observed Effect	Context/Condition	References
Estrogen	Modulates estrobolome via β-glucuronidase activity, affecting reabsorption.	Higher estradiol levels.	Premenopausal women.
Testosterone	Influences androgen metabolism and reduces inflammation.	Increased/sustained levels in males; Decreased levels in females with high androgens.	Aging males; Females with PCOS
Cortisol	Modulates the gut-brain-HPA axis and reduces systemic inflammation.	Decreased cortisol levels.	Individuals with chronic or acute stress
Insulin	Improves gut barrier function, reduces inflammation, and enhances SCFA production.	Improved insulin sensitivity and reduced resistance.	Individuals with insulin resistance, PCOS, or metabolic syndrome
Thyroid Hormones	Influences nutrient absorption and immune signaling via the gut-thyroid axis.	Reduced TSH, increased free T3/T4 (mixed findings).	Individuals with thyroid disorders (needs more research)

Effective Probiotic Strains and Lifestyle Factors

The effects of probiotics are highly strain-specific. For hormonal benefits, multi-strain supplements often containing Lactobacillus and Bifidobacterium species are frequently recommended. Some specific strains and combinations supported by research include:

Lactobacillus rhamnosus: Has shown benefits in improving sperm parameters and testosterone levels in animal models under stress, and is also linked to gut-brain axis effects.
Bifidobacterium longum: Associated with stress reduction and improved gut barrier function, which indirectly supports hormonal balance.
Lactobacillus acidophilus: Often included in multi-strain formulas for PCOS-related hormone and metabolic improvements.
Lactobacillus casei: Linked to improvements in insulin sensitivity in animal studies and hormonal profiles in women with PCOS.

In addition to probiotic supplementation, several lifestyle factors can significantly influence the gut-hormone axis:

Diet: Consuming a diverse, fiber-rich diet with prebiotics (found in fruits, vegetables, and whole grains) supports the growth of beneficial gut bacteria.
Exercise: Regular physical activity can positively influence gut microbiome diversity and function.
Stress Management: Chronic stress can negatively impact gut health and hormonal balance, so practices like meditation and yoga are beneficial.
Sleep: Poor sleep can disrupt the gut microbiome and hormonal rhythm, so adequate sleep is crucial.

Conclusion

Probiotics do not directly produce hormones, but they can significantly influence hormonal balance by modulating the gut microbiome. Through mechanisms like regulating the estrobolome, reducing inflammation, impacting the HPA axis, and producing beneficial compounds like SCFAs, specific probiotic strains can affect hormone levels such as estrogen, testosterone, cortisol, and insulin. While clinical evidence is promising for conditions like PCOS and stress-related hormonal issues, effects are highly dependent on the strain and individual. More extensive human trials are needed to standardize therapeutic protocols. A healthy gut, supported by probiotics and a balanced lifestyle, appears to be a key component of hormonal health.

For more information on the intricate relationship between the microbiome and sex hormone-related diseases, consult resources from the National Institutes of Health. [https://pmc.ncbi.nlm.nih.gov/articles/PMC8506209/]

Frequently Asked Questions

Yes, several studies indicate that probiotics can be beneficial for managing PCOS. They have been shown to help improve insulin resistance, decrease total testosterone, and increase sex hormone-binding globulin (SHBG), thereby positively influencing the hormonal profile associated with PCOS.

Probiotics affect hormones through several mechanisms. They can modulate the 'estrobolome,' the gut bacteria that metabolize estrogens; reduce systemic inflammation which can disrupt hormone signaling; influence the HPA axis to affect stress hormones like cortisol; and produce short-chain fatty acids (SCFAs) that impact metabolic and gut-brain signaling.

While some animal studies, particularly involving Lactobacillus reuteri, have suggested a link between probiotics and sustained testosterone levels in aging males, the evidence in humans is less robust. More research is needed to confirm this effect in men.

Strains from the Lactobacillus and Bifidobacterium genera are most commonly studied for hormonal effects. For example, L. reuteri is linked to androgen effects, and combinations of Lactobacillus and Bifidobacterium are often used in PCOS research.

Yes, research indicates that certain probiotics, sometimes referred to as 'psychobiotics,' can help lower stress-induced cortisol levels. This occurs through their influence on the gut-brain axis, potentially affecting mood and the HPA stress response.

The timeline for observing hormonal changes from probiotic supplementation is not fixed and varies based on the individual's condition, the specific hormones, and the strains used. Some studies in PCOS showed improvements after 12 weeks, while some meta-analyses on thyroid hormones suggest stronger effects in shorter durations (e.g., up to 8 weeks). Consistency and duration are key factors.

Research provides conflicting results on whether single-strain or multi-strain probiotics are more effective. Some studies suggest multi-strain combinations, especially with prebiotics (synbiotics), might offer broader benefits, while others find significant effects from single strains. The optimal choice depends on the specific hormonal imbalance and individual response.