People with ankylosing spondylitis may be more likely to receive a diagnosis of an autoimmune thyroid condition, such as Hashimoto’s disease.

Hashimoto’s disease, also known as Hashimoto’s thyroiditis, and ankylosing spondylitis are both autoimmune conditions. This means that they develop when the immune system attacks the body’s own tissues.

In Hashimoto’s disease, the immune system attacks and damages the thyroid gland, which can lead to hypothyroidism or an underactive thyroid. Hypothyroidism can cause fatigue and weight gain, among many other symptoms.

In ankylosing spondylitis, the immune system attacks the joints and ligaments in the spine. Common symptoms include back pain and stiffness. The condition may also cause inflammation in other joints and organs, such as the eyes.

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Some small studies have found an association between ankylosing spondylitis and autoimmune thyroid diseases, such as Hashimoto’s. People with one of these conditions may also have an increased risk of developing the other condition.

An older 2012 study evaluated the thyroid health of 108 people with ankylosing spondylitis and concluded that people with ankylosing spondylitis have an increased likelihood of having autoimmune thyroid disease.

Another study from 2014 evaluated Hashimoto’s disease more specifically. Researchers found that diagnosis of Hashimoto’s thyroiditis was “significantly higher” in participants with ankylosing spondylitis than control groups.

While these studies suggest that Hashimoto’s and ankylosing spondylitis may have links, there is a lack of high quality evidence to support these claims.

More research is necessary to determine whether ankylosing spondylitis directly contributes to thyroid issues, including Hashimoto’s disease. Shared genetic or environmental risk factors may account for the link between these two conditions.

Certain immune cells and processes appear to play a role in both diseases. These include tumor necrosis factor (TNF), a small protein that the immune system uses for cell signaling, which can drive inflammation.

Some research suggests that anti-TNF treatments may help prevent autoimmune thyroid disease in people with ankylosing spondylitis. Anti-TNFs are a class of biologic medications that help reduce inflammation in people with certain autoimmune conditions, including ankylosing spondylitis.

For instance, in the above 2012 study, people with ankylosing spondylitis were less likely to have autoimmune thyroid disease if they were receiving treatment with anti-TNFs.

A 2020 study also found that thyroid dysfunction was less common in people with ankylosing spondylitis who were receiving anti-TNF treatment compared with those who were taking nonsteroidal anti-inflammatory drugs (NSAIDs).

Hashimoto’s disease is not a connective tissue disease. However, it can cause muscle pain, joint pain, and other symptoms similar to certain connective tissue disorders.

People with Hashimoto’s disease show signs of connective tissue disease more often than the average person. These conditions include:

  • rheumatoid arthritis
  • psoriatic arthritis
  • lupus
  • Sjögren disease

Researchers in a 2017 study note that people with Hashimoto’s disease also have an increased risk of fibromyalgia. Several other autoimmune conditions, including rheumatoid arthritis and lupus, also increase the risk of fibromyalgia.

This chronic pain condition causes muscle and joint pain, tender points, and other symptoms.

Attending regular checkups with a doctor is important for people with Hashimoto’s disease or ankylosing spondylitis. A person should inform a doctor if they experience any changes in their health, even if those changes seem unrelated to their condition.

Autoimmune conditions such as Hashimoto’s disease and ankylosing spondylitis can affect multiple parts of the body. People with one autoimmune condition have an increased risk of developing another.

A person’s doctor may order tests to determine the cause of their symptoms. The doctor may then recommend changes to the person’s treatment plan, including their prescribed medication.

Treating ankylosing spondylitis may involve NSAIDs, biologics such as anti-TNFs, or other medications. To treat hypothyroidism from Hashimoto’s disease, doctors may prescribe the medication levothyroxine.

A person’s doctor may also recommend lifestyle changes to help manage the symptoms, reduce the risk of complications, and improve quality of life.