Reduced intestinal motility is one of the risk factors for development of a Small Intestinal Bacterial Overgrowth (SIBO). Hypothyroidism is associated with altered GI motility.

How Hypothyroidism And SIBO Are Connected

If you are a patient who has been diagnosed with hypothyroidism you may also suffer with constipation. But, did you know that constipation may promote bacterial overgrowth (SIBO) leading to chronic GI symptoms. SIBO is a common cause of not only chronic diarrhea but also chronic constipation. Your thyroid regulates all of your metabolic processes including gut motility. An under-active thyroid like we often seen in patients with Hashimotos thyroiditis, can slow down many aspects of digestion including intestinal motility. That’s why hypothyroidism so often causes constipation. When you are constipated and food lingers in your gut, it becomes a breeding ground for pathogenic disease causing bacteria.

Many hypothyroid patients also have a decreased level of HCL (Hydrochloric acid). HCL is the primary stomach acid that helps break down and digest proteins and fats. If you are low in HCL then you can’t properly digest your food, which allows allows bad bacteria to overgrow in your gut.

How SIBO Can Also Contributes to Hypothyroidism

Did you know that your gut and your thyroid depend on one another? Good gut health depends on good thyroid function and good thyroid function also depends on good gut health. Here’s why…. we often talk about thyroid hormones like T4, but a big problem for people with hypothyroidism is not poor production of T4 thyroid hormone bur rather poor conversion of T4 into T3 that causes low T3 hormone levels.

Twenty percent (20%) of your T4 (the storage form of thyroid hormone) is converted to T3 (the active form) in your gut. However, when and if your Gut flora is disrupted and it’s not functioning up to par, this conversion is reduced, leading to hypothyroidism symptoms and Low T3 or Low Free T3.

The good bacteria in your gut are also critical in preventing leaky gut, or intestinal permeability. Leaky gut occurs when the tight junctions of your small intestine open up, allowing toxins, microbes, and partially undigested food particles to escape via your bloodstream. A leaky gut can be the initial step for autoimmunity.

These particles (Proteins, Medications, Hormones, Food, Chemicals) are tagged as foreign invaders by your immune system, which sends a wave of inflammation to fight them off. Leaky gut is one of the primary triggers of autoimmunity, including the autoimmune form of hypothyroidism, Hashimoto’s. If your gut remains leaky, your immune system continues to attack your thyroid relentlessly, worsening thyroid dysfunction symptoms.

So Which Came First SIBO Or The Thyroid Problem?

As you can see, thyroid function and your microbiome are an interconnected ecosystem of their own. Which came first? thats a good question, but I’m not sure it matters. It’s kind of a chicken or the egg situation, where hypothyroidism contributes to bacterial overgrowth, and bacterial overgrowth worsens thyroid dysfunction. In some cases, the hypothyroidism comes first, and in others the thyroid dysfunction leads to SIBO. Since they go hand-in-hand so frequently, I highly recommend testing for SIBO if you have symptoms of both SIBO and hypothyroidism.

Interested in learning more about SIBO? Check out my 10 part video series here