Thyroid eye disease (TED) is a condition that can damage the tissues and muscles around your eyes. Your risk of developing TED is influenced by several factors. Some of these factors can’t be changed (known as nonmodifiable risk factors), while others can (known as modifiable risk factors).

Thyroid Eye Disease Is an Autoimmune Disorder

TED is caused by an autoimmune disorder, which means that your immune system mistakenly attacks your body. Normally, your immune system helps protect you by creating special proteins called antibodies. These antibodies fight off foreign invaders like viruses and bacteria that can make you sick.

Antibodies attach to these unwanted substances in your body and alert your immune system to attack and destroy them. If you have TED, your immune system begins making antibodies against the healthy tissues around your eye, signaling your immune system to attack.

TED can also develop if your body makes too much of a protein called insulin-like growth factor 1 receptor (IGF-1R). IGF-1R is involved in signaling pathways that contribute to immune system activity around the eyes.

However, researchers don’t fully understand how TED develops. They are still working to understand why some people develop TED and others don’t. They’re looking into genetics and environmental factors to learn more about how this disease starts.

Continue reading to learn more about the causes of TED and nine risk factors.

1. Graves’ Disease

Graves’ disease is commonly associated with TED. In fact, TED is also known as Graves’ eye disease or Graves’ ophthalmopathy. About half of people with Graves’ disease will develop TED at some point. However, only about 3 percent to 5 percent of people will develop severe symptoms related to TED.

Graves’ disease is an autoimmune condition that happens when your immune system attacks your thyroid gland. Your thyroid is a small gland found in the front of your neck that helps regulate your metabolism (how your body makes energy).

People with Graves’ disease make an abnormal antibody called thyroid-stimulating immunoglobulin. This antibody attacks the thyroid gland, resulting in hyperthyroidism (abnormally high levels of thyroid hormones).

Thyroid-stimulating immunoglobulin may also mistakenly recognize the cells around the eye. When this antibody recognizes a cell, it signals the immune system to attack, causing inflammation in the tissue around the eye.

Although Graves’ disease and TED are connected, they’re generally considered independent conditions. This means that the severity of Graves’ disease doesn’t always match the severity of TED. For example, someone could have mild symptoms of Graves’ disease but more severe symptoms of TED, or vice versa.

2. Female Sex

TED more commonly affects women and people assigned female at birth. One study in the journal Clinical Endocrinology found that females were four times more likely to develop TED compared to males.

TED may be more common in females because they also have an increased risk of autoimmune diseases associated with TED, such as Graves’ disease. Compared to males, females are about four times more likely to develop Graves’ disease.

Although females are more likely to develop TED, males and people assigned male at birth who develop TED may be more likely to experience more severe symptoms.

3. Middle Age

TED can occur at any age but tends to affect middle-aged adults. It’s most commonly diagnosed in people in their 40s and 60s.

Research has found that in women, TED is most likely to occur from ages 40 to 44 and from 60 to 64. In men, TED is most likely to develop from ages 45 to 49 and from 65 to 69.

Older adults may be more likely to experience more severe symptoms of TED compared to younger people.

4. Genetics

Your genes contain instructions for how your body should properly function. Mutations (abnormal changes) in your genes can create differences in how your body works.

Research suggests that your genes may play a role in how likely you are to develop TED. Changes in certain genes related to your immune system are linked to an increased risk of TED. If you have one or more of these gene mutations, you may not have any problems until an environmental factor (such as smoking) triggers it. Although your genetics are a nonmodifiable risk factor for TED, you may be able to control your exposure to modifiable risk factors, such as smoking. More research is needed to understand exactly which genes increase your risk and how much impact they have.

5. Smoking

Smoking cigarettes or other tobacco products is a well-known risk factor for TED. Smoking has been found to increase the risk of TED by seven to eight times.

Not only does smoking increase your risk of developing TED, but it’s also linked to more severe symptoms and a longer active phase of TED.

Smoking may also reduce how well certain treatments work. Compared to people who don’t smoke, those who smoke don’t respond as well to TED treatments, such as corticosteroids (medications that reduce swelling) and teprotumumab-trbw (Tepezza).

6. Radioactive Iodine Therapy

Radioactive iodine therapy is a treatment for hyperthyroidism and Graves’ disease. If your healthcare provider prescribes radioactive iodine therapy, you’ll take one dose of radioactive iodine as a pill or liquid. The radioactive iodine slowly destroys your thyroid gland over two to three months to reduce the amount of thyroid hormones that your thyroid makes.

About 1 in 4 people with TED who have radioactive iodine therapy will experience worsening symptoms. People who smoke are more likely to develop TED after radioactive iodine therapy. If you need this type of treatment, your healthcare provider may also prescribe a corticosteroid to reduce your risk.

7. Other Thyroid Problems

Although Graves’ disease is the most common thyroid problem associated with TED, people with other types of thyroid disorders can also develop TED.

Hypothyroidism (low levels of thyroid hormones), another condition related to TED, can develop if the thyroid gland is damaged or destroyed. This damage may also result from an autoimmune condition called Hashimoto’s thyroiditis. TED can also occur in people with normal thyroid hormone levels (also called euthyroid).

8. Other Types of Autoimmune Disorders

Graves’ disease isn’t the only type of autoimmune disorder associated with TED. People with other conditions — such as type 1 diabetes and rheumatoid arthritis — may also have an increased risk. This is likely because people with one autoimmune condition often develop others, including Graves’ disease.

9. Certain Vitamin Deficiencies

Selenium and vitamin D deficiencies have been associated with developing TED.

Selenium is an essential mineral that helps your immune system and thyroid function properly. Studies from the American Thyroid Association have found that people with Graves’ disease who have low levels of selenium may have an increased risk of TED.

Vitamin D is a nutrient important for the health of your bones and immune system. A 2020 study found that low vitamin D levels in people with Graves’ disease were linked to developing TED.

It’s important to understand the risk factors for TED to prevent and manage it effectively. Knowing how genetics and other health conditions interact can help people at risk take steps to lower their chances of developing TED. Being aware and catching the disease early can lead to better results, ease symptoms, and improve the overall quality of life for those living with the condition.

Talk With Others Who Understand

On TEDhealthteam, the social network for people living with thyroid eye disease and their loved ones, members come together to ask questions, give advice, and share their stories with those who understand life with TED.

Are you or a family member living with TED? Share your experience in the comments below, or start a conversation by posting on your Activities page.