Thyroid diseases and gut issues often go hand in hand. Not only do hormones produced by the thyroid affect digestive health, digestive issues can cause nutrient deficiencies that can impair the thyroid’s ability to produce these hormones.

In other words, poor gut health can suppress thyroid function, and poor thyroid function can lead to poor digestion, resulting in conditions such as gut inflammation and increased intestinal permeability (leaky gut).

When looking to improve thyroid function or address thyroid-related autoimmune conditions such as Hashimoto’s, it’s important to also look at digestive health. Our digestive system is connected to and has an effect on virtually every other system in the body, and healing the gut is often the first step in addressing other health conditions, including many thyroid conditions.

How does the thyroid work?

The thyroid is a butterfly-shaped gland located at the front of the neck, which produces important hormones that help manage and regulate many functions throughout the body, including metabolism, mood, energy levels, cellular repair, and digestion.

Low thyroid function, or hypothyroidism, can lead to symptoms such as fatigue, brain fog, difficulty losing weight, insomnia, dry skin, hair loss, and depression.

Why is gut health important for thyroid health?

The main hormone secreted by the thyroid is thyroxine, commonly referred to as T4. Thyroxine plays a vital role in heart and muscle function, brain development, and digestion. However, T4 is inactive, meaning cells in the body can’t use it directly. It must first be converted to an active form known as triiodothyronine, or T3.

Part of that conversion takes place in the gut, with the help of beneficial bacteria in the intestines. We talk about gut bacteria – AKA the microbiome – often, because it impacts our health in so many ways. The human gut is home to over 100 trillion microbes, which assist with numerous functions throughout the body. They help produce vitamins, protect against gut pathogens, and help regulate the immune system. They also provide enzymes that help break down and digest food.

Gut dysbiosis and digestive issues

However, many people suffer from gut dysbiosis, or an imbalance in intestinal bacteria. Dysbiosis occurs when harmful pathogens start to outnumber the beneficial bacteria. Microbiome dysbiosis can be caused by many factors, including poor diet (eating too much sugar and processed foods with artificial ingredients), excessive use of antibiotics, illness, use of nicotine, lack of exercise, and other lifestyle factors. Exposure to gut pathogens such as a food poisoning incident can also contribute to dysbiosis.

When gut bacteria become imbalanced, it can lead to symptoms such as fatigue, gas and bloating, inflammation, skin problems, and anxiety or depression. An imbalanced microbiome can also cause digestive issues, including a reduced ability to break down the foods we eat and absorb the nutrients they contain.

Low stomach acid

A lack of stomach acid is also a common digestive issue. Many people with heartburn take acid-reducing medications, which may temporarily improve symptoms, but can cause bigger problems over time. Low stomach acid – a condition known as hypochlorhydria – can lead to poor digestion and nutrient absorption, especially minerals, as well as an overgrowth of harmful bacteria.

Dysbiosis and thyroid hormones

Getting back to our thyroid hormones: T4 and T3 are made from the amino acid tyrosine – which we get from the protein we eat – and iodine, which is a trace element naturally found in some foods, such as seaweed and sea salt. The conversion of T4 into T3 also requires certain nutrients, including selenium and zinc.

If your microbiome is out of balance, you’re lacking digestive enzymes, or you have low stomach acid, you won’t be able to properly digest your food and absorb the vitamins and minerals you eat. In turn, your body won’t be able to produce T4 and convert it into T3, which means your thyroid function can falter.

Thyroid and leaky gut syndrome

T3 and T4 also help protect the mucosal lining of the gut. The lining of the intestines acts as a barrier, allowing nutrients to pass through and enter the bloodstream, while preventing the passage of larger molecules and harmful substances.

A lot of action happens at this barrier, which is a well-orchestrated passageway. Immune cells in the intestine sort and organize what is allowed into the bloodstream. Helpful nutrients are allowed to pass through special channels known as tight junctions, while harmful bacteria and potentially toxic molecules – such as those from artificial food ingredients – are blocked. When the immune cells sense an invader, they will dispose of it before it gets into the bloodstream.

When levels of these T3 and T4 are low, however, the tight junctions of the intestinal barrier become damaged or compromised, resulting in dysfunction. The intestinal barrier becomes “leaky,” meaning more things can pass through, such as undigested foods, toxins, bacteria, and artificial ingredients – things that should not be allowed to pass into the bloodstream. When this happens, the immune cells will respond with an inflammatory reaction, basically like an alarm saying “invader!” This is known as increased intestinal permeability, or leaky gut syndrome.

If not corrected, over time, this constant inflammatory response confuses the immune system into thinking everything is an invader. Although it starts in the gut, this inflammatory reaction ends up in the bloodstream and can travel through the body, causing inflammation everywhere – in joints, skin, the brain, and other organs – including the thyroid.

The thyroid is very sensitive to inflammation, which can suppress thyroid function, impair its ability to produce important hormones, and contribute to autoimmune conditions such as Hashimoto’s.

What causes leaky gut?

Many lifestyle and digestive factors can contribute to increased intestinal permeability, including:

Inflammatory foods such as processed foods, alcohol, and sugar
Changes to the microbiome from pathogenic bacteria (ie: food poisoning), yeast overgrowth, parasites, poor digestive function, and excessive antibiotics
Certain conditions, including inflammatory bowel disease, obesity, and nonalcoholic fatty liver disease.
High levels of cortisol caused by excess stress
Gluten sensitivity
Use of nonsteroidal anti-inflammatory drugs (NSAIDs)

Microbiome interaction with Hashimoto’s

Inflammation of the thyroid gland is related to conditions such as Hashimoto’s, an autoimmune condition where the immune system targets the thyroid gland, causing even more inflammation and interfering with thyroid function.

The gut microbiome plays a role in balancing the immune system. When the gut has too many harmful bacteria or not enough of the good bacteria, this environment sends inflammatory signals to the immune system. A healthy microbiome keeps balance by helping the immune system recognize what is a friend or foe. For someone with an autoimmune condition, the immune system has become confused and is now attacking the body, which should be considered a friend, not foe.

Can thyroid issues cause gut problems?

Not only can all of these digestive issues impair thyroid function; thyroid problems can also cause gut problems.

Hypothyroidism (low thyroid function) is the most common thyroid disorder. It slows down the digestive tract, leading to constipation, bloating, gas and heartburn.

Hyperthyroidism (overactive thyroid) speeds up the digestive tract, which can lead to diarrhea.

Can probiotics help your thyroid?

When microbiome imbalance is present, taking a probiotic may help improve thyroid function.

Probiotics can help reduce inflammation in the gut by promoting a more balanced microbiome ecosystem. They influence beneficial bacteria and tell the immune system to turn off the inflammatory response. With less inflammation in the gut, the intestine can repair a leaky barrier, which in turn helps reduce inflammation in the rest of the body.

Plus, less gastrointestinal inflammation and a more balanced microbiome will aid in the production of thyroid hormones and the conversion of T4 to T3.

Can healing your gut help your thyroid?

Intestinal inflammation is detrimental to thyroid health. Supporting gut issues such as digestion of your food, microbiome imbalance, and increased intestinal permeability can help your thyroid as well as a host of other systems and organs throughout the body.

How to improve your gut and digestion

If you have digestive issues or symptoms of a microbiome imbalance or leaky gut, take these steps to improve your gut health.

Reduce cortisol levels by managing stress. Meditation has been shown to reduce anxiety and depression, and make people more resilient to stress.
Reduce your intake of alcohol, refined carbohydrates, and sugar
Reduce the use of inflammatory vegetable oils, such as soy, corn, or canola
Quit smoking or using other nicotine products
Take a probiotic supplement or eat fermented foods
Eat plenty of anti-inflammatory foods such as dark leafy greens, berries, olive oil, wild fatty fish like salmon, green tea, ginger, and turmeric
If possible, and with your doctor’s approval, reduce your use of antibiotics, antacids, or NSAIDs

Supplemental nutrients that can help improve gut health

Digestive bitters, if needed, to help stimulate the production of stomach acid
Digestive enzymes
L-glutamine
DGL
Aloe vera
Zinc carnosine
Fish oil

Foods that contain nutrients helpful for thyroid health:

Bone broths for amino acids
Sea vegetables for iodine
Shellfish and pumpkin seeds for zinc
Brazil nuts and mushrooms for selenium
Colorful vegetables, fruit, spices and herbs for anti-inflammatory nutrients

Schedule a free 20-minute phone consult to learn how we can help support your digestion and thyroid issues.

Thyroid and Gut Health