Estrobolome: the little-known part of your microbiota involved in recycling your hormones

When we think about female hormones, we usually look at the ovaries, the menstrual cycle or menopause. Yet there is another piece of this story that lives in a seemingly unexpected place: our gut.

It is called the estrobolome, a functional part of the gut microbiota involved in processing estrogens, hormones that are essential throughout a woman's life.

Although there is still much to research, this set of microbial functions is helping to broaden our understanding of the relationship between the gut, hormones and women's health.

Because to understand how the body works, it is not always enough to study each system separately. We also need to understand how they communicate with each other.

What is the estrobolome?

The estrobolome is the set of microbial genes and their functions related to estrogen metabolism in the gut.

It is part of the gut microbiota ecosystem, made up of bacteria and other microorganisms that live in our digestive tract.

Some of these bacteria produce enzymes capable of modifying estrogens and their metabolites. Among them is beta-glucuronidase, which can help reactivate certain estrogens that the body had prepared for elimination.

This means the microbiota is not only involved in digestion. It can also influence the amount and type of estrogens that become available to the body again.

Research on the estrobolome is growing, although its specific effects on each woman's health are not yet fully understood.

Estrogen recycling: how does it work?

To understand it, it helps to follow the journey of these hormones.

1. The body processes estrogens

Estrogens are produced mainly in the ovaries during the reproductive years, although there are other sources, such as the adrenal glands and adipose tissue. The liver transforms them to make their elimination easier.

2. Some of these compounds reach the gut

Some estrogens modified by the liver are excreted through bile and pass into the gut. There they can be eliminated or undergo further transformations.

3. The microbiota can modify these compounds

Certain bacterial enzymes, such as beta-glucuronidase, can remove the chemical groups the body had added to facilitate the elimination of some estrogens.

4. Part of them can be reabsorbed

After this transformation, certain estrogens can regain their biological activity and be reabsorbed through the gut, returning to circulation. This process is part of what is known as enterohepatic circulation.

It is not that the gut makes all your hormones again, but that the microbiota can influence the fate of part of the estrogens the body is processing.

The intensity of this process depends on many factors, and there is no single estrobolome pattern that can be considered ideal for all women.

Why does it matter for women's health?

Estrogens take part in many physiological processes. Their activity is related, among other things, to bone health, the reproductive system and the regulation of various metabolic functions.

That is why understanding how these hormones are metabolised can provide relevant information about the interaction between the microbiota and female physiology.

The estrobolome is especially interesting in three areas.

1. Hormonal transition and menopause

During the transition to menopause, ovarian estrogen production declines and a woman's hormonal environment changes.

At the same time, the composition and functions of the gut microbiota may also change over the course of life. The relationship is bidirectional: hormones can influence the microbiota and the microbiota can take part in their metabolism.

Research is studying whether these interactions help explain some individual differences in health during perimenopause and postmenopause.

However, we cannot yet say that a particular estrobolome causes hot flushes, insomnia, weight gain or mood changes. These phenomena are multifactorial and require individual clinical assessment.

2. Estrogen metabolism

It is not only how much estrogen the body produces that matters. It also matters how it is transformed, how it is eliminated and how much becomes available again.

The microbiota is one of the elements involved in this process, together with the liver, hormone production, circulation and other physiological mechanisms.

Importantly, greater activity of certain bacterial enzymes is not necessarily beneficial or harmful in itself. Its meaning depends on the biological context and other factors still being researched.

So the goal is not to indiscriminately increase or reduce hormone recycling, but to better understand how it works within each woman's overall health.

3. Research on hormonal health and disease risk

The scientific community is also studying whether differences in the estrobolome may be related to estrogen-sensitive diseases, including breast cancer.

A review published in 2025 analysed studies on the microbial pathways involved in estrogen metabolism and their possible relationship with breast cancer. Its findings showed important limitations and differences among the available studies.

These findings must be interpreted with caution: an association between microbiota and disease does not prove that a specific alteration of the estrobolome is its cause.

Today, the estrobolome is a promising field of research, but on its own it is not a validated tool for diagnosing disease or calculating individual cancer risk.

Can we look after our estrobolome?

There is not yet a proven diet, supplement or probiotic that specifically optimises the estrobolome of all women.

What we can do is look after gut health within an overall prevention strategy.

• Prioritise a varied, fibre-rich diet. Vegetables, fruit, legumes, whole grains, nuts and seeds provide nutrients and substrates that can support different microbiota functions.
• Include a diversity of plant foods. Varying fibre sources helps provide different substrates to gut microbial communities.
• Look after digestive health. If there are persistent symptoms, relevant bowel changes or discomfort affecting quality of life, consult a health professional rather than automatically attributing them to hormones.
• Review supplements critically. Probiotics, products marketed for hormonal balance and other supplements are not interchangeable and do not all have the same evidence. Their usefulness depends on the product, the indication and the individual context.
• Keep an integral view of health. Diet, sleep, physical activity, medication, life stage and medical history are all part of the context needed to interpret hormonal health.

These measures support general and digestive health, but they do not guarantee a specific change in the estrobolome or replace indicated medical treatments.

Does an estrobolome test make sense?

It is an increasingly common question as interest in the microbiota and personalised medicine grows.

Commercial microbiota tests can describe certain microorganisms or functions, but that does not mean they all measure estrobolome activity in a validated way or that their results allow precise clinical decisions.

Research is still working to identify which microbial functions are relevant, how to measure them reliably and what they mean for people's health.

For now, there is no routine estrobolome test that can on its own establish a hormonal diagnosis, determine the cause of menopausal symptoms or guide a personalised treatment with proven efficacy.

Information from a test only gains clinical value when it can be interpreted together with symptoms, medical history, examination and other indicated tests.

At SHOMMA, understanding health means connecting the pieces

Women's health does not depend on a single hormone, a single organ or an isolated number in a blood test.

The estrobolome reminds us that the body works as a network of interconnected systems. Hormones influence the gut, the microbiota takes part in hormone metabolism, and both interactions happen within a biological context that changes throughout life.

At SHOMMA we champion an integral, preventive view of women's health: understanding each woman's life stage, interpreting clinical information with sound judgement and identifying which aspects deserve attention.

It is not about finding a single explanation for every symptom or turning every scientific discovery into a new test. It is about distinguishing what we know, what we are beginning to understand and what information can truly help make better decisions.

Because knowing your biology better is a way of caring for your health in the long term.

SHOMMA Healthspan Center Listen to your biology. Design your longevity.

Scientific references

• The estrobolome: Estrogen-metabolizing pathways of the gut microbiome and their relation to breast cancer.
• Gut microbial beta-glucuronidase: a vital regulator in female estrogen metabolism.