Connections Between The Gut And The Thyroid According To Experts

Connections Between The Gut And The Thyroid According To Experts

More than a thousand years ago, the Hippocrates said that all diseases really begin in the gut.


Today, studies are increasingly finding that this statement may be true, with scientific evidence pointing out that the general well-being of the gastrointestinal system seems to play a role in the regulation of the immune system and many other functions of the human body.


In fact, the health of the gut may even play a role in the effectiveness of certain pharmaceutical drugs used to treat some diseases1.


The same factors may apply when looking at the Thyroid gland. This gland is located in the neck of the human body and secrets hormones that play essential roles in regulating metabolism. These hormones are called Thyroxine and Triiodothyronine. The Thyroid gland makes more Thyroxine than Triiodothyronine, but Thyroxine is considered an inactive form of Thyroid hormone.


The body is able to convert Thyroxine hormones into Triiodothyronine, the active Thyroid hormone, however. In many cases, Thyroxine is also rather referred to as the prohormone of Triiodothyronine2.


This is where things get interesting – according to some of the more recent scientific studies that have been conducted, the gut may even have an impact on Thyroid health.


The connection may also go the other way around, however. In this post, we take a look at how gut health and Thyroid health are connected.


The Gastrointestinal Tract And Its Role In Health

We will start by taking a closer look at how the gastrointestinal tract really works and how it is related to the immune system, as well as the remainder of the body.


The gastrointestinal tract is actually a long tube – the tube starts at the mouth and then end at the ends. The mouth is where food enters the body, and the anus is where waste materials and any undigested food particles and other types of substances are excreted from the body.


While it is well-known that the gut is home to millions of microorganisms, collectively referred to as the microbiome or gut flora, many do not realize that an estimated 70% of immune cells and tissue that are present in body also sits in the gastrointestinal tract. This is known as the gut-associated lymphoid tissue, or sometimes just called the GALT.


The GALT that lies in the gastrointestinal tract plays a major role in the body, and any problems that occur with these immune tissues can actually result in disease. One scientific review paper3, led by a team at the University of Belgrade in Serbia, explains that recent studies have linked adverse effects with the gut-associated lymphoid tissue to many autoimmune diseases, due to the mechanisms of action that occur when problems develop with this system.


While multiple sclerosis is pointed out specifically in the study, there are many other autoimmune conditions that should be noted as well.


Different types of immune cells are stored in the lymphoid tissues that make up the GALT. B lymphocytes and T lymphocytes are only two examples of such immune cells. These cells are responsible for protecting the body by making antibodies that fight against the presence of antigens. Antigens are essentially types of molecules that are threats recognized by the immune system of the human body.


Now, this is where things can get complicated as well. In some people, a condition like leaky gut syndrome can cause certain proteins to escape from the gastrointestinal tract and, in particular, from the gut-associated lymphoid tissue – when the proteins escape from the gut, they enter the bloodstream.


While the leaky gut syndrome is sometimes not classified as an actual or official medical disease, there are various publications that have shown that this is something that the general public and even physicians should be concerned about. Essentially since when leaky gut syndrome occurs, a tear in the gastrointestinal tract’s wall develops – and then the content of the gut may slowly leak into the body.


Scientists in Virginia published a report in 20174 that explains how important it is to consider the possibility of leaky gut as a potential contributing factor toward the rising prevalence of autoimmune diseases in the modern day.


The question now is, how do leaky gut and other issues with the gut-associated lymphoid tissue really contribute to the development of autoimmune diseases. The issue that should be addressed here is the protein molecules that tend to leak into the blood circulatory system when such a condition becomes present.


While these proteins tend to have their functions within the lining of the gastrointestinal tract, the moment they start to enter the bloodstream, they are in a location within the body that is not considered “normal” – the protein molecules do not belong in the blood circulatory system. For this reason, the immune system starts to recognize the proteins as pathogenic substances or a threat to the body.


This essentially results in the immune system producing antibodies to target the proteins that have now entered the bloodstream. As the proteins collect in certain parts of the body, the immune system will ultimately attack healthy tissue – and this is how the connection with autoimmune conditions come up.


Autoimmune conditions involve an incorrect response from the immune system – this happens when antibodies are created to attack tissue that is actually healthy and a “normal” part of the body, but the immune system recognizes these cells or tissue as foreign threats.


How The Gut Affects Thyroid Function

As we have mentioned already, when an issue like leaky gut develops, it often causes certain proteins to leak into the bloodstream. The immune system then recognizes the proteins as a threat to the body’s health and starts to produce antibodies, which then attacks the proteins.


Several studies have found that this type of issue may actually have an impact on the Thyroid gland – in particular, this raises the opportunity for the development of a condition such as Hashimoto’s disease5. Hashimoto’s disease is an autoimmune condition where healthy Thyroid tissue is attacked by the immune system.


When a person develops Hashimoto’s disease, they are likely to suffer from a condition known as Hypothyroidism6. The condition is sometimes referred to as Hashimoto’s thyroiditis or autoimmune Thyroid disease. Worsening symptoms of Hashimoto’s disease are known as Hashimoto’s flare ups.


While a leaky gut has been associated with autoimmune conditions affecting the Thyroid, this is not the only way that the well-being of the gastrointestinal tract affects the gland. Various studies have found that the microbiome of the gut tends to play a role in the endocrine system. The endocrine system is a collection of glands that produce hormones in the body. The Thyroid gland forms part of this particular system.


A study7 published in the Journal of Current Microbiology, conducted in 2014, scientists actually found that people who have a Thyroid disorder tend to have an alteration in the diversity and number of certain microorganisms that reside in their digestive system – when compared to healthy individuals who do not suffer from such conditions.


In particular, the study found that individuals who had a condition known as Hyperthyroidism had an increase in the number of Enterococcus bacterium species that resides in their gastrointestinal tract. On the other hand, the number of Lactobacilli and Bifidobacteria bacterium species seemed to be lower in those with Hyperthyroidism, compared to individuals with a healthy Thyroid gland.


Hyperthyroidism And Hypothyroidism

To better understand the impact of the gut on the Thyroid gland, it is important to recognize the two conditions that have been associated with problems that present in the digestive system.


It seems like an issue like leaky gut may lead to an autoimmune response that ultimately contributes to Hypothyroidism. Inadequate maintenance of healthy gut flora, on the other hand, seems to contribute to Hyperthyroidism. Let’s consider each of these conditions independently and look at symptoms that a patient should recognize.



Hypothyroidism is a very common form of Thyroid disease. In this condition, there is a reduction in the number of Thyroid hormones that are present in the patient's body. There are two types of Hypothyroidism, including8:


  • Primary Hypothyroidism
  • Secondary Hypothyroidism


Due to the impact that these Thyroid hormones play in the body and metabolism, a number of adverse effects may be experienced.


In the majority of patients, fatigue and tiredness will be some of the most common symptoms experienced in the presence of Hypothyroidism. Weight gain is another symptom that is very common among individuals with this Thyroid disease.


In addition to these symptoms, the patient may also experience the following complications:


  • Hoarseness
  • Muscle weakness
  • A puffy face
  • Dry skin
  • Constipation
  • Maybe more sensitive to temperature when it is cold
  • High cholesterol
  • Muscle aches
  • Muscle stiffness
  • Joint pain and inflammation
  • Joint stiffness
  • Thinning hair
  • Impaired memory function
  • A slower heart rate


Some women tend to find that their menstrual periods become heavier than usual and irregular when they develop Hypothyroidism. The condition has also been linked to a higher risk of depression, which would be another symptom to be on the lookout for, especially if the above-mentioned symptoms are also present.


It is important to recognize Hypothyroidism early on. Failure to undergo treatment may result in certain complications, including more severe joint pain, heart disease, and even obesity. The condition may also have an adverse impact on fertility.



Hyperthyroidism is another condition that affects the Thyroid gland. In this case, however, there is usually an elevation in the number of Thyroxine and Triiodothyronine that is present in the patient’s body. This causes metabolism to speed up and leads to other health problems.


In many cases, the patient will start to lose weight without going on a diet or changing their exercise habits. Fatigue and general weakness also tend to develop when a patient has Hyperthyroidism.


Other symptoms that may signal the presence of this particular Thyroid disease include:


  • Increased sweating
  • More frequent bowel movements than usual
  • Intolerance to heat
  • Nervousness
  • Anxiety
  • Agitation
  • Heart palpitations
  • An irregular heartbeat that is also faster than usual
  • Tremors
  • Restlessness
  • An increase in appetite
  • Hair may become brittle


Hyperthyroidism can also be caused by an autoimmune disease. In such a case, the condition is known as Graves’ disease.


Another issue that patients with Hyperthyroidism may experience is sleep disturbances. Menstruation may also become irregular in women who develop the condition. In some cases, there may also be mental complications that develop in the presence of too many Thyroid hormones in the blood, such as difficulty concentrating.



Thyroid hormones are crucial for metabolism and many other functions in the human body. Thyroid hormone receptors have been found in various tissues throughout the body.


Understanding underlying factors that contribute to Thyroid-related problems, such as the development of conditions like hypothyroidism, plays a role in providing patients with a more effective treatment plan.


New studies have linked problems with gut health to a higher risk of autoimmune conditions that affect the Thyroid, ultimately implicating its ability to produce the right hormones.



1 G.B. Hatton, C.M. Madla, S.C. Rabbie, A.W. Basit. All disease begins in the gut: Influence of gastrointestinal disorders and surgery on oral drug performance. 5 Sep 2018.


2 G.A. Brent. Mechanisms of thyroid hormone action. The Journal of Clinical Investigation. 4 Sep 2012.


3 Multiple Authors. Gut-associated lymphoid tissue, gut microbes, and susceptibility to experimental autoimmune encephalomyelitis. Journal of Beneficial Microbes. 3 Feb 2016.


4 Q. Mu, J. Kirby, C.M. Reilly, X.M. Luo. Leaky Gut As a Danger Signal for Autoimmune Diseases. Frontiers In Immunology. 23 May 2017.


5 M.C. Arrieta, L. Bistritz, J.B. Meddings. Alterations in intestinal permeability. BMJ: Gut Journal. Oct 2006.


6 H.E. Takami, R. Miyabe, K.Kameyama. Hashimoto’s thyroiditis. World Journal of Surgery. May 2008.


7 Multiple Authors. Gut Microbe Analysis Between Hyperthyroid and Healthy Individuals. Springer Link: Journal of Current Microbiology. Nov 2014.


8 I. Kostoglou-Athanassiou, K. Ntalles. Hypothyroidism – new aspects of an old disease. Hippokratia: Quarterly Medical Journal. 2010.

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