Understanding the Gut-Hormone Connection | Daily Dose - Physician's Choice
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  • December 21, 2020 7 min read

    When we talk about hormones, we’re usually talking about the endocrine system. This system comprises several glands, including the thyroid, adrenal glands, and reproductive organs. 

    Increasingly, researchers and experts have introduced the gut microbiome into discussions of hormonal health. In fact, some believe the health of the gut microbiome may be the single most important factor when it comes to hormonal balance (1)

    The careful balance of hormones at play in the body is often likened to an orchestra; if one instrument (or hormone) is out of tune, the entire symphony is affected. 

    When following this analogy, the gut microbiome can be thought of as the conductor (2). Microbes within the gut are responsible for producing hormones themselves. They also communicate with various glands throughout the body, regulating which hormones should be produced and released. 

    The gut microbiome plays a role in producing, regulating, and balancing hormones—from estrogen and testosterone to melatonin, stress hormones, and thyroid hormones. These hormones, in turn, influence everything from mood to motivation to metabolism.

    Supporting a healthy gut can help with hormonal balance. Avoiding gut-dysbiosis triggers (an imbalance within the gut microbiome) like refined sugar, chronic stress, and certain medications is one vital step to take. High-quality probiotic supplements can also support a healthy gut microbiome and hormonal balance. 

    Estrogen, the gut, and the estrobolome 

    The importance of estrogen 

    Estrogen is one of the most familiar and essential hormones in the body. It’s the primary female sex hormone, but it’s required by both men and women in proportion to levels of other sex hormones like progesterone and testosterone. 

    The role of estrogen extends well beyond reproductive function and the menstrual cycle, contributing to cardiovascular health, body fat regulation, and cognitive function (3, 4, 5)

    We all need estrogen for these and other essential functions, but it must maintain balance with other hormones. Both excessive and insufficient estrogen levels can contribute to a myriad of health problems and increase chronic disease risk. 

    Meet the estrobolome 

    How does the body regulate estrogen levels, you might ask? Largely, with the help of the gut microbiome. 

    More specifically, with the help of a particular group of gut microbes referred to as the estrobolome. The microbes that make up the estrobolome have the ability to produce estrogen and signal to the rest of the body to ramp up production as needed (6)

    These gut microbes can also metabolize excess estrogen, keeping levels from getting out of hand (7). This is important, as too much estrogen can lead to health issues, including weight gain, irregular or painful menstrual cycles, and mood dysregulation. 

    Excess estrogen may also increase the risk of developing certain kinds of cancer and conditions like endometriosis.

    When there is an imbalance within the gut microbiome (known as gut dysbiosis), the estrobolome may be affected. This can lead to insufficient or excessive estrogen levels, thereby disrupting hormonal balance and increasing the risk of developing estrogen-related health conditions (8).  

    Woman out in the desert enjoying the sunshine

    The estrobolome in postmenopause 

    In women, estrogen levels fluctuate throughout the menstrual cycle and decrease naturally with age and in menopause. In postmenopause, reduced estrogen levels may contribute to an increased risk of obesity, cardiovascular disease, and osteoporosis, as estrogen helps regulate fat storage and metabolism, heart health, and bone health (9, 10, 11).

    Gut dysbiosis may further disrupt estrogen levels, potentially worsening the problem (6, 10). Imbalances within the gut microbiome may also contribute to the risk of obesity, cardiovascular disease, and osteoporosis in other ways (12, 13, 14)


    Polycystic Ovary Syndrome (PCOS) is a common female hormonal condition marked by an imbalance between estrogen and androgens (male sex hormones). Researchers have found an association between PCOS and alterations in the gut microbiome. Recent animal studies have shown that modulating gut bacteria can help balance estrogen and androgens, suggesting that restoring the health of the gut microbiome may help manage PCOS (6, 15)


    Endometriosis, another common condition among women of reproductive age, occurs when endometrial tissue erroneously grows outside of the uterus (16). Excess levels of circulating estrogen underlie this condition. 

    Recent research suggests that women with endometriosis may have alterations in their estrobolomes that would favor increased estrogen production. As a result, researchers conclude that gut dysbiosis may be a significant factor in the development of the condition (17)

    The gut microbiome, estrogen, and cancer 

    Gut dysbiosis has been implicated in different types of cancer over the last several years (18). In hormone-sensitive cancers such as breast cancer, impaired estrogen metabolism due to gut dysbiosis may be a contributing factor (6)

    Beyond the gut, women with breast cancer often have different bacteria makeups in their breast tissue than healthy women, including higher levels of potentially damaging bacteria (19). The breast tissue of healthy women has been shown to have more beneficial bacteria strains, including Lactobacillus

    As an oral probiotic supplement, Lactobacillus has been shown to reach the mammary gland (20). Future studies will likely explore the possibility that supplementation with Lactobacillus-containing probiotics can not only modify the composition of the gut microbiome but also supply beneficial bacteria to the breast tissue, where it may have an anticarcinogenic effect (21, 22)

    Similarly, both excess estrogen and gut dysbiosis have been linked to prostate cancer development and progression in men (23, 24)

    Testosterone and the gut 

    Just as estrogen levels naturally decrease in women as they age, testosterone levels (the primary male sex hormone) decrease naturally in men (25)

    The gradual lowering of testosterone levels is normal, but factors like inflammation, diabetes, or hypertension can exacerbate the decline and lead to a deficiency (25, 26)

    Low testosterone can occur at any age and may cause symptoms including fatigue, depression, low libido, increased risk of obesity, and bone loss. 

    Recent research has linked gut dysbiosis and increased intestinal permeability to lower testosterone production (27, 28).

    Man standing outside near mountains watching the sunset

    The gut and the thyroid 

    A growing body of research highlights the significance of gut health related to thyroid disorders (29).

    Thyroid disorders are typically autoimmune in nature (30). This means the thyroid itself may be healthy, but something is going wrong with the immune system, causing it to attack the body’s own tissues (including the thyroid). 

    Autoimmune conditions in general, and autoimmune thyroid disorders specifically, have been linked to gut issues, including increased intestinal permeability (also known as “leaky gut”) (31). Increased intestinal permeability can cause bacteria and food particles to “leak” into the bloodstream, prompting an immune response that can get out of control. 

    Gut dysbiosis and low microbiome diversity are also linked to thyroid disorders, including hypothyroidism (32)

    To learn more about this relationship, read our piece on the thyroid-gut connection.  

    Melatonin and the gut 

    Melatonin, sometimes referred to as the sleep hormone, plays a key role in regulating the sleep-wake cycle.  

    The body requires sufficient levels of the mood-influencing neurotransmitter serotonin (sometimes referred to as the “happy chemical”) to produce the melatonin we need to fall and stay asleep. 

    Bacteria in the gut produce more than 90% of your body’s serotonin, which is part of the reason a balanced and healthy gut microbiome is so essential for mental health as well as for sleep quality (33)

    The connection between sleep quality and gut health appears to go both ways. Poor sleep habits or an irregular sleep schedule can disrupt the gut microbiome, just as gut dysbiosis can lead to dysregulated melatonin levels and poor sleep quality (34)

    Stress hormones and the gut 

    Epinephrine (adrenaline) and norepinephrine thrive in situations of acute stress (for example, an emergency or a job interview). However, when levels of these hormones are chronically elevated, it can lead to anxiety or depression, among other concerns. 

    Certain kinds of pathogenic gut bacteria including E. coli and Salmonella have been linked to chronically elevated levels of norepinephrine and epinephrine (35)

    Chronic stress also contributes to gut dysbiosis, increased intestinal permeability, and other gut health issues, creating a vicious cycle when gut imbalances and excessive stress are not addressed (36)

    Healing the gut for hormonal balance

    Given the growing body of research linking gut bacteria to hormonal health, identifying and repairing any imbalances within the gut is an essential first step towards achieving and maintaining hormonal balance (37, 38)

    The gut microbiome may be in a state of dysbiosis with or without the presence of digestive symptoms. Certain kinds of stool tests can provide insights; however, you can take many steps at home to support healthy gut bacteria without those. 

    To support the health of the gut and the endocrine system, try to limit refined sugar, excessive stress, and the use of certain kinds of medications, including NSAIDs (Advil, Aleve) and antibiotics (39, 40, 41, 42)

    Xenoestrogens (foreign estrogens), chemicals that are close enough in structure to estrogen to mimic it in the body and contribute to dysbiosis and hormonal imbalance, should also be avoided as much as possible. 

    Xenoestrogens are found in certain plastic products, pesticides, skincare products, and cleaning products. There are accessible, natural alternatives to most xenoestrogen-containing products. 

    Probiotics for gut and hormone health

    Supplementation with probiotics (beneficial bacteria) may restore balance to the gut microbiome, thereby helping to restore hormonal balance. Probiotic supplements that contain prebiotics (food for beneficial bacteria) may be especially helpful. 

    Animal studies of probiotics for estrogen-related conditions including PCOS, endometriosis, and menopausal osteoporosis have been promising and will help set the stage for future clinical trials in humans (43, 44, 45)

    Studies have also shown that probiotic supplementation can help to improve thyroid function, balance stress hormones, and regulate melatonin (46, 47, 48)

    In summary

    Hormonal balance is essential for overall health. Hormones are produced and released by various glands throughout the body, as well as by bacteria within the gut.

    Gut bacteria are responsible not only for producing hormones but also for signaling to glands when they should be releasing hormones, and for metabolizing excess hormones. 

    Often, when hormones are imbalanced, the root cause lies within the gut microbiome. In fact, researchers are increasingly exploring the gut microbiome as one of the most important factors in hormonal balance. 

    The gut plays a vital role in the production and regulation of hormones, including estrogen, testosterone, thyroid hormones, stress hormones, and melatonin. These hormones influence mood, cognitive function, sleep quality, weight, reproductive health, and chronic disease risk, to name a few. 

    Factors that contribute to gut dysbiosis include diet, stress, and certain kinds of medication. To achieve and maintain hormonal balance, make restoring your gut health a top priority.

    Ellie Ellias - Contributing Writer, Physician’s Choice 

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