Several studies shed light on the intimate connections between the gut and thyroid disease.

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What Does the Gut Have to Do with the Thyroid?

There has always been a direct relationship between the thyroid and the gut, so it’s not surprising that infections, inflammation, or changes in the gut environment can also affect thyroid function.

In my functional medical practice, I specialize in both thyroid and gut issues, seeing many cases of thyroid autoimmunity and small intestinal bacterial overgrowth (SIBO). This post will examine several scenarios in which thyroid autoimmunity and gut infections, such as SIBO and others, go hand in hand.

Let me first define thyroid autoimmunity, which is the main driver of hypothyroid disease in the Western world. The most common form of thyroid autoimmunity is Hashimoto’s. Hashimoto’s is an autoimmune disease in which the body makes antibodies or immune cells that attack and damage the thyroid. If this process occurs long enough, this could lead to irreparable damage to the thyroid gland and it will become hypothyroid.

People diagnosed as hypothyroid do not have adequate levels of thyroid hormone in the blood. In this case, thyroid replacement medication is needed, at least in the short-term, to stabilize the body and thyroid condition.

Hypothyroid symptoms can vary, but the main ones are fatigue, dry skin, heart palpitations, constipation, restlessness, fluctuations in mood, vertigo or dizziness, hair loss, restlessness, wheezing, difficulty swallowing, and pain in the front of the throat or the sensation of something stuck there. Having three or more of the symptoms is associated with the risk of a thyroid condition, but the main three symptoms must include fatigue and dry skin among them to point at hypothyroid disease.

Thyroid hormone regulates the metabolism of cells, speeding them up or slowing them down according to the levels present.

Hypothyroid patients often experience feeling cold, dry, slow, and constipated, while hyperthyroid patients feel the opposite.

When thyroid issues are treated with medications but not much improvement is seen, it’s always advisable to look at the gut.

Identifying and treating infections such as SIBO and H. pylori can help improve thyroid function and symptoms.

One study showed that treatment of H. pylori can improve thyroid autoimmunity. Two groups of patients who had both Hashimoto’s and H. pylori were studied. One group was treated for H. pylori and the other group was not. The group that was treated saw improvement in their thyroid antibodies.

It can also work the other way around. A study looked at 1800 patients with SIBO to see what conditions increased chances of SIBO. They looked at factors like abdominal surgery, acid suppressing medications, immunosuppressant medications, and hypothyroid patients who were and were not on meds.

Surprisingly, the highest risk group for SIBO was people in the hypothyroid group. And the biggest among them were the hypothyroid patients that were on medication. This does NOT mean that getting off your thyroid meds is a good idea!

Let’s look at how SIBO can be a risk factor for developing hypothyroid disease by examining one hypothesis.

Some evidence shows that intestinal bacteria utilize selenium. When bacterial populations grow, as in the case of SIBO, there’s an increased demand for selenium, which may lead to selenium deficiency in the host.

We also know that selenium deficiency is an underlying factor that contributes to thyroid autoimmunity. A trial where people with thyroid autoimmunity took supplemental selenium saw a marked improvement in thyroid autoimmunity levels.

So it may be the case that bacterial overgrowth creates the condition of selenium deficiency that underlies hypothyroid disease, like Hashimoto’s.

Does that mean that supplementing selenium can also feed and increase bacterial overgrowth in the case of SIBO?

Probably not.

Clinical trials did not show notable signs of increased bacterial overgrowth, which is characterized by symptoms such as bloating, gas, constipation, diarrhea, or abdominal pain.

The takeaway is that selenium supplementation is likely to be safe for someone with both SIBO and thyroid disease.

So if you have thyroid autoimmunity, look towards gut health for improving the immune system and related symptoms. And remember that sometimes the symptoms we think are coming from the thyroid are actually based in the gut. Managing and exploring gut health is a crucial part of successfully managing hypothyroidism and thyroid autoimmunity.

If you need help with thyroid or digestion, click here.
To be notified when my print book becomes available & get a free gut health eBook, click here.
If you are a healthcare provider looking to sharpen your clinical skills, click here.

What do you think? I would like to hear your thoughts or experience with this.

Dr. Ruscio is your leading functional and integrative doctor specializing in gut related disorders such as SIBO, leaky gut, Celiac, IBS and in thyroid disorders such as hypothyroid and hyperthyroid. For more information on how to become a patient, please contact our office. Serving the San Francisco bay area and distance patients via phone and Skype.