A hormone, a gut, and a thyroid are linked together.

The Link Between IBS and Thyroid Disorders

Last updated: April 2023

Your thyroid is an important gland that plays a crucial role in metabolism and growth. If the body needs more energy, for example during pregnancy, the thyroid gland makes more hormones.1

An overactive thyroid is referred to as hyperthyroidism, which happens when the thyroid produces too many hormones. Hypothyroidism or an underactive thyroid occurs when there are not enough hormones being produced. Hashimoto’s disease is a common cause of hypothyroidism and is an auto-immune condition where the immune system attacks your thyroid gland.1

Importance of the gut and the microbiome

The human body is home to trillions of microorganisms and most of these organisms are known as the gut microbiome which usually lives with us in a harmonious way. The gut microbiome is mainly comprised of bacteria but also includes other organisms such as fungi and viruses.2

The microbiome has been identified as an important factor in health and is linked to many diseases. An imbalanced microbiome increases the risk of Hashimoto’s thyroiditis and Graves’ disease.2

Gut bacteria can influence the availability of minerals that are important for thyroid health, such as iodine, selenium, and zinc. In existing thyroid disorders, the microbiome can affect the uptake of medications.2

An imbalanced microbiome can contribute to gut inflammation and the presence of intestinal permeability, otherwise known as leaky gut. The gut houses a large proportion of the immune system. Therefore, if the gut isn’t healthy it can lead to high levels of inflammation. This ongoing inflammation and immune system activation can lead to immune system dysfunction, where it can end up attacking your own tissues.2

Research has also shown that patients with thyroid disease have different types of gut bacteria, with less beneficial bacteria present.2

The link between hormones, gut, and thyroid health

Hormones can also impact thyroid health. Estrogen has an indirect effect on thyroid function by increasing thyroid binding globulin, which binds thyroid hormones to the necessary tissues. It also increases the need for thyroid hormone in people with hypothyroidism.3

Gut bacteria can increase estrogen levels in the body by recycling estrogen and by making estrogen type end products.4


Small intestine bacterial overgrowth (SIBO) is a major cause of IBS and is common in patients with hypothyroidism. SIBO can contribute to thyroid dysfunction by increasing inflammation, damage to the intestine and reduced absorption nutrients. SIBO is also linked to lowered levels of thyroid hormone receptor expression and an imbalance of gut bacteria.2,3

Tips for supporting gut and thyroid health

  • If you have IBS it is worthwhile investigating if you have SIBO. If you do have SIBO, then work on clearing the overgrowth and address the underlying cause of SIBO can help restore your gut health.
  • Identifying and removing food sensitivities such as gluten will help to reduce inflammation.
  • Remove processed foods and excess sugar
  • Replace unhealthy foods with a balanced diet that will provide your body with the nutrients your thyroid needs to function properly.
  • Working with a qualified health professional can help you make sure you are eating the right diet to support both your gut and your thyroid.

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The IrritableBowelSyndrome.net team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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