SIBO and Thyroid dysfunctions

Are you suffering from symptoms such as fatigue, brain fog, mood swings, dry skin, slow bowel movement, and even weight gain? These could also be a sign of thyroid dysfunction. ^{(1, 2, 3, 4, 5, 6)} Your thyroid is responsible for controlling your metabolic processes. If it is under-functioning (in the case of hypothyroidism), it pushes the brake pedal and slows down the body's metabolic processes. In the case of hyperthyroidism, it pushes the gas pedal and makes the process run faster.

Even though you may have thyroid dysfunction, your thyroid-like symptoms can actually stem from your gut. On the other hand, low functioning thyroid could also be a risk factor for Small Intestinal Bacterial Overgrowth (SIBO). It means that SIBO can lead to a hypothyroidism state, but hypothyroidism can also result in bacterial overgrowth.

The gut-thyroid connection

Some studies have found that thyroid symptoms improved after treating the gut. These gut issues can come from Helicobacter pylori ^(7,8), parasites ⁽⁹⁾, fungal infection (Candida) ⁽¹⁰⁾, SIBO ^(11), or food intolerances ⁽¹²⁾, etc.

Studies estimate that around 30% of people with hypothyroidism have low stomach acid ⁽¹³⁾. Stomach acid is essential to kill pathogens and prevent the overgrowth of bacteria. If this protective mechanism fails, then it can easily lead to SIBO. ⁽¹⁴⁾ This is why using stomach acid blockers (Proton-pump inhibitors) unnecessarily can be problematic and may also lead to SIBO. Here you can read more about the types of SIBO.

The other reason is that overgrowth of bad bacteria can lead to issues with the conversion of thyroid hormones, namely T4 (inactive form) to T3 (active form). ⁽¹⁵⁾ Much of the thyroid hormone is released by the thyroid gland in the inactive type known as T4 (thyroxine), but it must be converted to an active form known as T3 (triiodothyronine) for the cells to use it. ⁽¹⁶⁾ Around 20% of T4 can be converted to T3 in the gut by good gut bacteria.

But most of the conversion is done by the liver, which can also be sluggish for many reasons. A sluggish liver and gallbladder cannot remove hormones efficiently, such as estrogen. Elevated estrogen levels can also negatively influence the conversion rate of thyroid hormones. ⁽¹⁷⁾

The other issue can be when T4 converts to reverse T3 (rT3), the inactive form. A higher level of reverse T3 can be produced if someone went through a major life event, a trauma (emotional or physical stress like a surgery), or having chronic stress (illness, inflammation). ^(18,19) In some cases, other factors such as diet, not just a diet high in sugars and processed foods, but also a ketogenic or very low carb diet, can cause elevated levels of rT3. ^{(20, 21)}

So making sure that you have a well-functioning gut and liver, the gallbladder is vital to ensure proper conversion of thyroid hormones.

The immune system-thyroid connection

There are 70% of the body's immune cells located in the gut. The immune response in this part of the body is called GALT, or gut-associated lymphoid tissue. The GALT contains several forms of immune cells, such as T and B cells, that detect and respond to antigens as potential threats that trigger immune system reactions.

Problems arise when any one of these intestinal barriers is weakened. When the small intestine's tight junctions loosen (in case of "leaky gut syndrome"), undigested food particles, microorganisms, toxins, or larger proteins enter the bloodstream. The immune system sees these particles as unwanted intruders and starts an inflammation process to rid of them. Leaky gut can be one of the underlying causes of autoimmune diseases, such as Hashimoto-Thyroiditis, an autoimmune form of hypothyroidism. If you have a leaky gut, the immune system can keep attacking the thyroid and cause continued problems. ^{(22, 23)}

What might help to support your body?

Focusing on gut health is an essential part of any treatment process as it is also connected to your immune system and thyroid autoimmunity, and thyroid functions. But concentrating on the thyroid function is also crucial.

If you are experiencing symptoms of thyroid dysfunction and SIBO, you can do the following steps:

1. Do the necessary testing to find out what the issue is behind your symptoms: ask for a SIBO breath test and a full thyroid panel from your Practitioner
2. Taking thyroid medication may help with motility and considering eliminating SIBO or other infections if present
3. Choose a customized diet that eliminates inflammatory foods such as sugar, processed foods, gluten, refined carbohydrates, refined oils, artificial sweeteners, etc.
4. Eat a whole food diet – including organic meats, vegetables, fruits, nuts, seeds based on your tolerance
5. Apply lifestyle changes that help you manage your daily stress
6. Take intestinal lining healing nutrients, boost motility

*This post is only for informational purposes; and not meant to diagnose, or treat any disease. I advise consulting with your healthcare practitioner regarding any treatment options or dietary changes.