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Guillermou's avatar

The microbiome affects the proper functioning of the thyroid gland, and the existence of the gut-thyroid axis is analyzed in the context of both thyroid diseases and gut dysbiosis.

Thyroid and gut diseases predominantly coexist: Hashimoto's thyroiditis (HT) and Graves' disease (GD) are the most common autoimmune thyroid diseases (AITDs) and often coexist with celiac disease (CD) and non-celiac wheat sensitivity (NCWS). This can be explained by damage to the intestinal barrier and the consequent increase in intestinal permeability, which allows antigens to pass more easily and activate the immune system or cross-react with extraintestinal tissues, respectively. Dysbiosis has not only been found in AITDs.

The gut is a target organ for thyroid hormone (TH), which exerts its action through the thyroid hormone receptor α1 (TRα1) expressed on intestinal epithelial cells. Alteration of intestinal microbial homeostasis (dysbiosis) is associated with autoimmune thyroid disease (AITD), including Hashimoto's thyroiditis, Graves' disease, and Graves' orbitopathy.

The gut microbiota largely regulates the homeostasis and development of immune cells. It modulates both the innate and adaptive immune systems, even outside the gut, and is fundamental in the development of gut-associated lymphoid tissue (GALT), where more than 70% of the entire immune system resides. GALT plays an important role in the development of tolerance to self-antigens by controlling their toll-like receptors (TLRs) in the intestinal mucosa.

There is a positive correlation between the concentration of short-chain fatty acid butyrate and the number of regulatory T cells (TREGs), which are key mediators of immune tolerance, as well as with lower concentrations of pro-inflammatory Th-17 cells. SCFAs can strengthen intercellular tight junctions in conjunction with thyroid hormones. The immune system itself influences the composition of the gastrointestinal microbiota, underscoring the symbiotic relationship.

Probiotics have demonstrated beneficial effects in thyroid diseases and may have a positive effect on trace elements such as selenium, zinc, and copper. Furthermore, microbes function as a reservoir of T3 and can prevent fluctuations in thyroid hormone levels, thus potentially reducing the need for T4 supplementation. The importance of maintaining a healthy gut microbiota stems from the fact that increased intestinal permeability due to dysbiosis allows lipopolysaccharides from gram-negative bacteria to enter the bloodstream and contribute to thyroid gland destruction. Small intestinal bacterial overgrowth (SIBO) has also been shown to be more frequently observed in autoimmune hypothyroidism. There is also a potential role for interference between the host and the microbiota in thyroid cancer.

https://www.mdpi.com/2072-6643/12/6/1769 (2020).---

https://www.mdpi.com/2077-0383/10/16/3609 (2021).---

https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.977587/full (2023).---

https://core.ac.uk/download/pdf/580113119.pdf#page=24 (2023).--

https://sirpublishers.org/index.php/jams/article/view/548 (2024).--

https://academic.oup.com/endo/article-abstract/165/1/bqad184/7458951?login=false (2024).---

Just steve's avatar

As with nearly every corner of our Society over the past half century or more, corruptions have pushed our focus to a narrow area and such keeps us from seeing the larger picture. We could very well build an artificial Mount Everest out of the many diets, diet books and programs. As have so many suffered over the years, while yes people lost weight - but only to gain it all back. More troubling, also gaining health issues. I used Keto at one point and did lose weight, this was interrupted by life demands. Now when able to resume more focus on myself, this newer information hits the target with the most centered not on just losing weight - but instead learning how to feed to create what should be our birthright - a healthy body all while gaining a healthy waistline getting there. Feed the body the proper proportions of Healthy Carbs, Proteins and Fat at a reduced rate to move the weight down then slowly increasing these to fine tune what our actual calory needs are to maintain our best health. Being thin for appearances is not a given for being healthy. A body able to perform as needed, to have its many tools to perform properly in all areas of our being, physical, mental and emotional, whether young, old, active physical workers, or athlete's - is.

wns115's avatar

Dr Mercola - GREAT article. There are still a few missing pieces.

I strongly invite you to consider an interview with "Healthy Gut Girl" Kitty Martone. I took an 8-week health course with her and learned more than I learned in 10 years regarding metabolism, thyroid, microbiome, negative impacts of strict diets, benefits of pro-metabolic diets,(as well as extreme rigidity that negatively impacts health even when applied to pro-metabolic diet).

She also had immense information on meds/supplements and cautions to watch out for based on the MDs she worked with - I believe you would LOVE talking to her. You both agree on about 85% but there is about 15% of 'new' material that could benefit (like best ways to take progesterone based on real data, lab testing results, and thousands of users' direct feedback.