Written by Dr. Bharat Pothuri, MD, FACG

How Gut Health Affects Your Thyroid

A Simple Guide

Your gut does more than just digest food. It also plays a big role in keeping your thyroid healthy. The gut and thyroid are closely connected. When your gut is unhealthy, your thyroid may not work properly.

This guide will explain how your gut affects your thyroid, and what you can do to support both.

What Is the Gut-Thyroid Connection?

The gut and thyroid talk to each other through what's called the gut-thyroid axis. Here’s how they work together:

• The gut helps absorb nutrients like iodine, selenium, and zinc. These are needed to make thyroid hormones.
• Your gut health affects your immune system. This matters because many thyroid problems are autoimmune diseases.
• The gut helps activate thyroid hormones, especially converting T4 (inactive) to T3 (active).

How Gut Bacteria Help the Thyroid

1. Helps With Nutrient Absorption
   Good gut bacteria help you absorb nutrients that are vital for thyroid function:
   • Iodine – Needed to make thyroid hormones.
   • Selenium – Helps convert T4 to T3.
   • Zinc – Supports immune and hormone function.
2. Supports Your Immune System
   Around 70% of your immune system is in your gut. If your gut is imbalanced, your immune system can become overactive and attack your thyroid. This can lead to autoimmune conditions like Hashimoto’s disease or Graves’ disease.
3. Activates Thyroid Hormones
   Your gut helps your body turn T4 (a storage form of thyroid hormone) into T3 (the active form). Without this process, your body can't use the hormone properly.

Signs Your Gut May Be Hurting Your Thyroid

• Constipation or diarrhea
• Gas or bloating
• Fatigue or brain fog
• Hair loss or dry skin
• Weight gain or weight loss

If you notice these, talk to a doctor. A gut issue may be behind your thyroid symptoms.

Gut Problems Linked to Thyroid Disorders

Hashimoto’s Disease:

This is the most common cause of hypothyroidism. People with Hashimoto’s often have less gut bacteria diversity. Their gut lining may also be “leaky,” letting bad substances into the body.

Graves’ Disease:

This causes hyperthyroidism. It’s also linked to gut bacteria changes. Studies show that people with Graves’ often have more harmful gut bacteria and less good bacteria.

Source: Study on Gut and Thyroid Autoimmunity – PMC

How to Support Your Gut and Thyroid

1. Eat a Gut-Friendly Diet
   • Fiber-rich foods: oats, beans, apples, and bananas
   • Fermented foods: yogurt, kefir, kimchi, sauerkraut
   • Healthy fats: avocado, olive oil, fatty fish
   • Protein: lean meats, eggs, and legumes
   • Selenium-rich foods: Brazil nuts, sunflower seeds
   • Iodine-rich foods: seaweed, iodized salt
2. Take Probiotics (with Doctor’s Advice)
   Probiotics can help balance your gut. Look for strains like:
   • Lactobacillus rhamnosus
   • Bifidobacterium lactis
   They may also help reduce inflammation and boost nutrient absorption.
   Source: Probiotics and Thyroid Function – Frontiers
3. Manage Stress
   High stress harms gut bacteria. Try:
   • Deep breathing
   • Yoga or walking
   • Journaling or meditation
4. Exercise Regularly
   Moving your body helps digestion and boosts thyroid hormone use.

Final Thoughts

Your gut health matters more than you think—especially for your thyroid. By eating well, managing stress, and taking care of your gut, you may improve thyroid function and feel better overall. If you’re unsure where to start, talk to a healthcare provider. They can help you create a plan that works for your body.

About the Author

Dr. Bharat Pothuri is a Board-Certified Gastroenterologist and Hepatologist. With extensive experience in digestive health, he specializes in advanced endoscopic procedures, chronic GI disorder management, and preventive care. Dr. Pothuri is dedicated to providing expert, patient-focused insights to help improve gut health and overall well-being.