Understanding the Thyroid-Gut Axis: How Gut Health Affects the Thyroid

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If you’re wondering, “Does gut health affect the thyroid?” the short answer is yes, but an adequate explanation is more involved than you might suppose. Recent explorations into the power of gut health have revealed very specific mechanisms for its influence. 

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When the bacteria inhabiting your body (the microbiota) are thriving, they support the thyroid gland, helping to ensure its proper function. When the gut bacteria are compromised, thyroid health diminishes accordingly.

What follows are a few ways poor gut health negatively affects the thyroid.

#1: It May Trigger Autoimmunity

While a definite causal link has not been identified, it is widely theorized that compromised gut health may contribute to the development of thyroid autoimmunity (Graves’ or Hashimoto’s). 

Poor dietary habits, certain medications, and a stressful lifestyle all contribute to a weakening of the microbiome, a critical layer of protection between the interior and exterior of the small intestine, where nutrient absorption occurs. When this is damaged, bacteria and toxins can leak into the abdomen, creating an environment that is chronically inflamed, as the immune system seeks to remedy the situation. 

The longer this inflammation persists, the more difficulty the immune system has distinguishing between self cells and pathogens. Thyroid autoimmunity occurs when this dysregulation leads to the immune system attacking the thyroid.

#2: It Influences Nutrient Availability

A leaky gut, described above, cannot absorb nutrients efficiently. Many vitamins and minerals are needed for the thyroid to synthesize thyroid hormones and convert them to a usable form. They are also critical for regulating the immune system and thus preventing autoimmunity that targets the thyroid. Essential nutrients for thyroid health include: 

• Iodine: Three or four iodine atoms make up the main structure of thyroid hormones. Without enough iodine available, thyroid hormone synthesis cannot proceed.
• Selenium: Selenium is incorporated into proteins that help convert inactive thyroid hormone (T4) to its active form (T3), and neutralize the oxidative stress resulting from thyroid hormone production.
• Zinc: This element is a cofactor for the production of thyroid-stimulating hormone and the conversion of T4 to T3.
• Iron: This element is necessary for the function of thyroid peroxidase, the enzyme that adds iodine to the thyroid hormone molecule during synthesis.
• Vitamin D: This vitamin is crucial for immune system regulation. Deficiency may be one factor in the development of thyroid autoimmunity.



#3: It Plays a Role in Thyroid Hormone Conversion

The conversion of thyroxine (T4) to its active form, triiodothyronine (T3), is essential for its use by the body’s cells. This conversion occurs via deiodinases primarily in the kidneys, liver, muscles, and brain, but studies indicate that these enzymes are also present in the intestinal tract. Besides this, a healthy gut can more adequately absorb other minerals necessary for T4-T3 hormone conversion. Therefore, any diminution in gut bacteria could result in a lower overall level of activated thyroid hormone.

The link between the thyroid and the gut is complex and not fully understood, but it is clear that what affects one affects the other. Thyroid dysfunction can impact the gut in the following ways. 

#1: By Hindering Saliva Production

Xerostomia, or dry mouth, is a common complaint of individuals with thyroid dysfunction, particularly hypothyroidism. This may be due to the slower metabolism resulting from insufficient thyroid hormone or a direct autoimmune attack on the salivary glands.

Saliva initiates the process of digestion by way of its component enzymes (amylase to break down carbohydrates, lingual lipase to break down lipids, and more). If the initial stages of digestion are not carried out in the mouth, the following difficulties may arise:

• The stomach and small intestine must work harder to digest food.
• Ingestion of oral bacteria disrupts the microbiome of the lower digestive tract.
• Digestive inefficiency results in poor nutrient absorption.

#2: By Decreasing Gastrointestinal Motility

Slowed metabolism also negatively impacts peristalsis, the movement of the muscles within the walls of the GI tract to propel food forward. When this movement slows, so do gastric emptying and elimination of waste, leading to:



• Bloating
• Abdominal discomfort
• Poor nutrient absorption

#3: By Hampering Liver Function

There is a significant association between hypothyroidism and the following difficulties with the liver, and each has a notable impact on the gut microbiota:

• Ineffective lipid metabolism: Excess lipids can alter the microbial environment of the gut, leading to gut dysbiosis.
• Non-alcoholic fatty liver disease: This condition alters the proportion of bacterial species present in the gut, and these changes have the potential to cause leaky gut and chronic inflammation of the intestines.
• Gallstones: By interrupting the flow of bile, gallstones can hinder lipid digestion and lead to chronic gut dysbiosis.

#4: By Compromising the Pancreas

Few organs are spared the widespread consequences of thyroid dysfunction. In a patient with hypothyroidism or hyperthyroidism, the pancreas runs its own risks of hazards, including:

• Pancreatitis
• Insufficient enzyme secretion
• Insulin insensitivity and diabetes
• Poor nutrient absorption

Due to its integral role in digestion, any impairment of the pancreas can have adverse effects on gut health.

Many symptoms of thyroid conditions can mimic those of gut health problems. If you are experiencing any of these, consult with your healthcare provider for a more comprehensive evaluation to determine the real cause of your symptoms:



• Brain fog
• Constipation or diarrhea
• Unexplained weight loss or gain
• Fatigue
• Depression
• Headaches

A condition initially affecting the thyroid may look suspiciously similar to a gut issue, but treating it as such will not ultimately solve the problem. Schedule a visit to HealthierU for help unraveling the mystery of what is causing your symptoms.

Dietary Changes

The best dietary habits to prioritize for a healthy gut are as follows:

1. Avoid ultraprocessed and fried foods.
2. Limit sugars and artificial sweeteners.
3. Focus on whole grains, fruits and vegetables, and fermented foods.

Probiotics & Supplements

While nutrients are best coming from the food you eat, you may find it necessary to supplement in order to get adequate amounts of selenium, zinc, iron, iodine, vitamin D, probiotics, etc. 

Supplementation should only be done in consultation with a healthcare provider who can evaluate your current levels of the abovementioned vitamins and minerals, so as to avoid the risk of overdose.

Lifestyle Changes

Your gut is sensitive not just to what you feed it, but also to other factors in your daily life. Regular exercise, adequate sleep, and low stress are all necessary for optimal gut health.

While some aspects of your lifestyle may seem beyond your control, cultivating the following habits can be a powerful way to regain command over your well-being:



• 2–3 hours per week of moderate to intense activity
• A bedtime routine that prepares you for 7–9 hours of sleep
• Stress-relieving activities such as hobbies, hiking, yoga, etc.

Whether your health issues are primarily gut-related or thyroid-related, you can benefit from the holistic services provided by Dr. Donna Sergi at HealthierU. 

Because these conditions can reinforce each other, the initial problem can be difficult to nail down, and you may feel as if you’re caught in a vicious cycle. Dr. Sergi’s hypothyroidism treatment in Brooklyn factors in all the elements of your particular health situation, so that you receive the most personalized health advice to help resolve your complaints. 



In keeping with her commitment to a natural, non-toxic approach to wellness, Dr. Sergi offers her support through professional nutrition and lifestyle guidance, along with her expertise in various health concerns, including:

• Acne
• Lower back pain
• Thyroid dysfunction 
• Menopause
• Hormonal imbalances
• Hair loss
• And more
  
  

Contact us today to schedule your first free visit and learn more about HealthierU’s superior services.