If you have been suffering from gut issues, whether they only started a few months ago or they have been going on for years, it is worth looking in to your thyroid health as there is a strong connection between the gut and the thyroid.

How Does My Thyroid Affect My Gut Health?

Constipation: Chronic constipation affects 9-20% of adults in the U.S (1). Constipation wreaks havoc on your microbial balance and dysbiosis (when your gut flora is out of balance) can cause constipation. 

The thyroid gland plays a major role in gut motility. It makes sense then, that when the thyroid is functioning sub-optimally, the gut will also slow down. The longer stool sits in the GI tract, the colon will actually resorb water from the stool as well as toxins. So, not only does your stool become hard and difficult to pass, your body is left with the choice of having the liver process those toxins yet again or storing the toxins in your body fat where your other organs are safe from them. 

Diarrhea: While chronic diarrhea is not as widespread as chronic constipation, it’s effects can be extremely damaging. One side effect is malabsorption, which can lead to nutrient deficiencies. 

Having a hyperthyroid (over-active) can cause the gut motility to move too fast. Not only will the affected person have to pass stools more frequently, but often they develop nutrient deficiencies because the body doesn’t have time to absorb nutrients effectively before they leave the body. The body isn’t the only one missing out on nutrients, however. The beneficial bacteria in your colon need ample time to feed on the food you provided them. If the food moves to quickly through the colon, they can starve and die off leaving more pathogenic bacteria to flourish. Counterintuitively, diarrhea can be a consequence of constipation. Reactive diarrhea happens when the colon is blocked by hard stool and the person eats again. That food has to sit too long in the GI tract. The fats rancidify, the carbs ferment, and the proteins putrefy. The result is that once the hard stool is finally passed, there will be diarrhea. Often there is foul smelling gas as well. 

Irritable Bowel Syndrome (IBS): IBS is the most common gastrointestinal disorder worldwide. Its prevalence is estimated between 10 and 15% (3). Typical symptoms of IBS include diarrhea (often at night), weight loss, vomiting, difficulty swallowing, iron deficiency anemia, and persistent pain that doesn’t resolve with the passing of gas or stool. There is sometimes rectal bleeding as well. (4)

Thyroid and Gut health connection

  • Intestinal Permeability: Thyroid hormones (T3 and T4) have been when to protect the gut from stress and they influence the tight junctions in the stomach and small intestine. So, if your thyroid isn’t functioning properly, this can lead to inflammation and leaky gut. 
  • Thyroid hormone conversion: 20 percent of the conversion from inactive T4 to Active T3 occurs in the digestive tract and therefore, gut dysfunction can be a major player in thyroid dysfunction.
  • Gut inflammation: When the gut is inflamed, whether by eating foods the body is sensitive to, dysbiosis, or gut motility issues, cortisol (the stress hormone) elevates. Cortisol decreases active T3 levels and increases levels of inactive T3.
  • Nutrient deficiencies: poor digestion, inflammation, leaky gut, and gut motility issues can lead to nutrient deficiencies. If the thyroid doesn’t have the nutrients it needs to perform optimally, then it will slow down and this can affect digestion, leading to worsening nutrient deficiencies. This can become a vicious cycle

Why do Conventional Treatments for Constipation, Diarrhea, and IBS Often Fail?

Conventional doctors will typically prescribe or recommend a laxative when it comes to treating constipation. Although a laxative can generally provide relief in the short term, in the long-term it can actually make the problem worse because they can actually impede your colon’s ability to move the stool along on its own. 

To treat diarrhea, doctors often recommend an anti-diarrhea medication such as Imodium. Unfortunately, the list of side effects from anti-diarrheal medication is long. It includes constipation, abdominal pain, nausea, vomiting, dizziness, fainting, drowsiness, and many more. 

When treating IBS, conventional doctors seem to be at a loss. Most recommend laxatives or antidiarrheals depending upon what symptoms are presenting. Pain medication (with its own list of side effects) may be prescribed to help with the hallmark abdominal pain symptoms. 

Thyroid hormone testing

Many conventional doctors only run one lab marker (TSH) when looking for thyroid imbalance, which often leaves thyroid imbalance undiscovered because TSH can come back in range when other biomarkers are out of balance. To find out if an underactive thyroid is causing or exacerbating your constipation make sure your doctor runs a full thyroid panel. 

The same holds true if an overactive thyroid is causing diarrhea. 

A Conventional Interpretation of a Thyroid Panel vs. an Integrative interpretation:

Conventional thyroid lab ranges for TSH is considered normal from 1-4. A functional or integrative physician considers the optimal range to be between 1-2! Why the discrepancy? The conventional “normal” range was created by averaging any patients who had their thyroid tested at that particular lab, whether their thyroids were functioning optimally or not.  

Biomarkers for a full thyroid panel 

  • TSH: 1-2
  • Reverse T3: 14.9-26.7
  • Free T3: 3-3.25
  • Free t4: 1-1.5
  • T4, total: 7.5-8.1
  • T3, Total: 90-168
  • T3 Uptake: 27%-37%
  • TPO antibodies: negative or positive
  • TGB antibodies: negative or positive

What is thyroid hormone?

The thyroid is a gland that primarily supports your metabolism. It takes iodine and tyrosine (an amino acid) and turns them into thyroid hormones. Many of your bodily functions are controlled by these thyroid hormones: Thyroxine (T4) and Triiodothyronine (T3) 

The H-P-T (hypothalamus-pituitary-adrenal) axis is what governs your production of thyroid hormones. Upon receiving a message from your hypothalamus (the master gland) that your body needs more thyroid hormones, your pituitary will send a message to the thyroid by releasing thyroid stimulating hormone (TSH). The thyroid in turn will upregulate its production of thyroid hormones. 

Thyroid Hormone Conversion: 

While T4 is the most plentiful hormone, T3 is the active hormone and as such is much stronger. T4 must be converted to T3 for the body to be able to use it. About 60% of this conversion occurs in the liver. 20% of this conversion happens in the digestive tract and the rest occurs in other body tissues. 

Natural Health Strategies for Gut-Thyroid health

  • Add a spore-based probiotic and fermented foods/beverages to your routine: Since long-term constipation or diarrhea can lead to dysbiosis, as discussed above, it is helpful to replenish your beneficial gut bacteria. Taking a spore-based probiotic is one of the fastest ways to do this. As a side benefit, most people find that it helps with their gut motility as well! Adding fermented foods and beverages is another step you can take to help rebalance your microbiome.
  • Start taking a motility activator: A motility activating supplement (which is different from a laxative) can help with both diarrhea and constipation and is great for those with IBS or SIBO as well. This supplement is far different from laxatives which can often cause rebound constipation. This supplement stimulates peristalsis, the rhythmic squeezing of your colon.
  • Stool testing: If you have had gut motility problems for more than a year, there is a god change that your microbiome is out of balance (dysbiosis). A test such as the GI Map can let you know what pathogenic microbes are lurking in there and your practitioner can create a protocol to rebalance your microbiome. Since 80% of the immune system is believed to be housed in the gut, this is something that should be taken seriously. 
  • Consider a restrictive diet: Making sure you’re are not eating foods you are sensitive to is a crucial step in gut healing because eating these foods causes inflammation and can lead to intestinal permeability (aka leaky gut). Your integrative practitioner can order a food sensitivity test for you so that you can eliminate the foods that aren’t good for your body right now. Another option is to follow a restrictive diet like Paleo, Autoimmune Paleo, or the Wahl’s Diet. These diets remove the most common food sensitivities and many people find their health improving dramatically as a result. 
  • Iodine: Iodine is often deficient in those with thyroid disorders. Iodine has an important role to play, not only in thyroid function, but also in digestion. It is concentrated in the salivary glands and in the gastric mucosa (the lining of mucus in your gut). If your doctor determines that you are deficient in iodine, you can supplement as well as increase your intake of iodine rich foods such as seaweed, seafood, grass-fed dairy, and pastured eggs. If an autoimmune thyroid condition is suspected, however, only supplement with iodine while under your doctor’s supervision.
  • Selenium: This mineral is critical for converting T4 to T3. It is also necessary to absorb iodine properly, so if you have a selenium deficiency, you will be unable to utilize your dietary iodine even if your intake is adequate. 
  • Zinc: Zinc is a critical mineral for digestion. If you don’t have enough zinc, your body can’t make enough digestive juices and it will not be able to break down and utilize the minerals in your food. As we saw above, iodine and selenium are crucial to thyroid health, so if you are doing the work to increase these minerals in your body through diet or supplementation, you will not want to overlook your zinc status. 
  • Aloe vera: Drinking aloe vera juice is soothing to the digestive tract, so it can be helpful for IBS. It is also anti-inflammatory. Aloe also can have a laxative effect without the bad side effects. 
  • L-glutamine: Glutamine is used by your gut to maintain and repair the lining (5). You can buy l-glutamine in capsule form or in a powder which can be easily added to smoothies and protein shakes. 
  • Fiber: Eating adequate fiber feeds your microbiome and binds toxins in your colon to prevent them from getting resorbed. You may need to start slow, especially if you are still dealing with constipation. Always make sure to drink plenty of water when increasing your dietary fiber to prevent an exacerbation of constipation. 


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