Hormones & Cycles

Your gut and your hormones

The realization that gut bacteria influence you in many ways is actually nothing new. The tiny microbes in your intestines take care of your metabolism, digestion and even influence your mood and mind. Find out what this has to do with your hormones and why your intestine is also called "the second brain" here.

The bacteria of your intestine

Your intestines are home to billions of bacteria and that's a good thing. In fact, about 100 billion intestinal bacteria live in a unique microorganism. They are located in the mucous membranes of your intestinal walls and need an acidic environment to perform their tasks. Researchers also call this construct microbiome. The hype about intestinal bacteria and a balanced intestinal flora is currently greater than ever.

By intestinal flora we mean here the totality of all bacteria and microorganisms contained in your intestine. In the meantime it is known how important the microbiome in our intestines actually is and how far-reaching the influence on the overall health of the human being is: The microbes are not only digestive helpers that process the food we eat, they also support the entire immune system and are closely related to our own mood and the production of important neurotransmitters in the brain.

Because of all these functions, the intestine and the microorganisms living in it are also known as the "super organ".

The human body as a whole resembles a large living community: billions of microorganisms live on the skin, in the intestines and in many other parts of the body. There is increasing evidence in studies that the composition of the intestinal microbiome is one of the factors that determines whether someone is healthy or sick, gains weight and feels depressed or mentally balanced.

The largest hormonal gland in the body

The intestine not only produces hormones, it is also the largest hormone gland in the body. In the wall cells that line the digestive tract, the so-called enteroendocrine cells (EEC) are scattered everywhere. Although they make up less than one percent of all enterocytes (or hemocytes) in the human intestine, they are the largest endocrine gland in the body. But when viewed as a whole and with the abundance of messenger substances they release - more than 20 hormones are known - the intestine breaks all records. Some of these hormones do not only aim at hunger or satiety. The hunger signal ghrelin, for example, clearly influences our behaviour. It can reduce anxiety but can also put some people in a much more aggressive mood.

Your digestive system throughout the cycle

Most women know that their digestion is also influenced by their cycle. Frequently, just before or during menstruation there is increased bowel activity or even diarrhoea. Of course, this has a logical background- after all, menstruation is meant to cleanse. While the old uterine membran loosens and is expelled, the whole body is in cleansing mode. What’s no longer needed gets released so that new cells can rebuild themselves and your body can start a new cycle.

During this cleansing process, toxic substances can be excreted from the intestine in particular, which can burden or influence our immune system. The entire metabolism is also running at full speed and the detoxification organs, such as the liver, gall bladder and kidneys, are doing the hardest work. The hormones progesterone, which is elevated especially in the second half of the cycle, and prostaglandins (tissue hormones) also affect the digestive system. They can cause flatulence, a feeling of fullness, mood swings, sleep disorders, water retention and much more. All symptoms you may experience as part of PMS (premenstrual syndrome).

Influence of intestinal bacteria on hormone balance and fertility

Inflammatory bowel diseases, diabetes, obesity, skin diseases and allergies - many human ailments have been linked to changes in the intestinal microbiome in recent years.

By pointing to an interaction between hormones and intestinal bacteria, scientists are now bringing another disease into play: the Polycystic Ovary Syndrome (PCOS). PCOS affects around ten percent of all women worldwide and is characterised by, among other things, elevated levels of male sex hormones. These lead to excessive male body hair, acne, but also to hair loss. The menstrual period can become irregular or stop altogether. And it can lead to the eponymous "polycystic" ovaries (ovaries), which have many follicle vesicles. Women with PCOS often have fertility problems, i.e. they cannot get pregnant, are often significantly overweight and have an increased risk of type 2 diabetes, but also depression and anxiety disorders, among other things. Find out more about PCOS here.

In a pilot study, scientists of the Medical University of Graz examined women with PCOS and compared their intestinal microbiome with that of healthy subjects. It was shown that both the number and the type of microbes correlated with the symptoms and hormonal changes in PCOS. The permeability of the intestinal wall and inflammatory factors in PCOS were also related to microbial diversity. Based on the study results, it can be assumed that the composition of the microbiome also has an influence on our sex hormones and their function. Up to now, PCOS has been treated mainly by weight reduction and hormone therapy. But if the findings of the pilot study are confirmed in larger studies, the use of pre- or probiotic therapeutics could be considered in order to positively influence the intestinal flora.


Lisa Lindheim et al.: Alterations in Gut Microbiome Composition and Barrier Function Are Associated with Reproductive and Metabolic Defects in Women with Polycystic Ovary Syndrome (PCOS): A Pilot Study. https://doi.org/10.1371/journal.pone.0168390

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Hormones & Cycles

Your gut and your hormones

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