Causes and Risk Factors of Hashimoto’s Disease

Hashimoto’s disease, also called Hashimoto's thyroiditis, is an autoimmune disease. Autoimmune diseases are a result of the body’s immune system attacking healthy issues because it thinks they are diseased. With Hashimoto’s, immune cells are attacking the thyroid gland. This attack causes inflammation and impairs the thyroid’s ability to make enough thyroid hormone.

Researchers don’t know why this happens, but they think genetics might be to blame and risk is higher for people with a family history of autoimmune and thyroid conditions.

Genetics

There are several inherited genes associated with Hashimoto’s disease, but the two most common are HLA-DR3 and HLA-DR5. These genes are more common in Caucasians. Having one of these genes doesn’t mean a person will definitely develop Hashimoto’s, it just means their risk is increased.

Relatives of people with Hashimoto’s also have a higher risk for developing the disease. And because it’s more common in women, female relatives have the highest risk. First degree relatives, especially children, have a higher incidence—up to nine times—for having the condition. There is also greater incidence of Hashimoto’s in twins than the general population.

Autoimmune Diseases

Having another autoimmune disease is a risk factor for developing Hashimoto’s disease. The opposite is true as well, and certain autoimmune diseases are associated with Hashimoto’s, including celiac disease, type 1 diabetes, and alopecia.

Thyroid Antibodies

Thyroid antibodies are common in people with Hashimoto’s disease. Often times, antibodies associated with this condition can be elevated for years before a diagnosis of Hashimoto’s is made. Elevated levels may appear normal in testing. However, it is a matter of time before the thyroid can no longer produce enough hormone.

While the majority of people with Hashimoto’s disease have specific antibodies, about 5 percent have no measurable thyroid antibodies. People without antibodies tend to have a milder form of the condition.

Lifestyle Risk Factors

There are many lifestyle factors that contribute to the development of Hashimoto’s disease, specifically smoking and stress.

When the body isn’t getting the nutrients and other essentials it needs for optimal function, it overcompensates from other body systems, especially the immune system, which overacts in response.

Gender

Hashimoto’s disease predominately affects more women than men. Researchers think that sex hormones play a role. Some women also develop thyroid problems during the first year after having a baby. Those types of thyroid issues tend to resolve, but it is possible for some of these women to develop Hashimoto’s later in life.

Age

The chances of developing Hashimoto’s disease increase with age. The risk is even greater for women, people with a family history of the condition, and anyone with an autoimmune disease.

Menopause

Decreased estrogen levels during menopause may affect thyroid function. 

However, they were unsure exactly what the connection was and noted further study was needed.

Environmental Risk Factors

Bacterial Infections

Much like other autoimmune diseases, Hashimoto’s may be triggered by a number of parasitic, yeast and fungal bacterial infections that start in the gastrointestinal tract. A person does not necessarily have to experience symptoms to be affected by these types of stomach bacteria. 

Unfortunately, much of the research on a Hashimito’s-infection connection isn’t specific enough to determine how exactly bacterial infections can trigger autoimmune thyroid diseases and/or how to reduce risk factors.

Excessive Iodine

Excessive iodine has been speculated to trigger Hashimoto’s disease and other types of thyroid disease. In one study of the New England Journal of Medicine, researchers from China looked at thyroid effects of iodine supplements. The researchers found giving iodine to the study participants who had adequate and excessive iodine levels increased the risk for autoimmune thyroid disease.

Radiation Exposure

Research has found a link between exposure to radiation and Hashimoto’s disease. The disease is common in those who have been exposed to radiation for cancer treatment. Moreover, it is common in those exposed to radiation from nuclear events.

A Word From Verywell

It is difficult to determine which risk factors will put a person at the greatest risk for Hashimoto’s disease. Genetics are the highest risk factors but often, the disease is caused by factors a person cannot prevent. Anyone who has a family history of Hashimoto’s or other autoimmune diseases can reduce their risk by making healthy lifestyle choices, including avoiding smoking, getting enough sleep, managing stress, eating a healthy and balanced diet, and being active.