What is Hashimoto’s Thyroiditis?

Hashimoto's thyroiditis,¹ also called Hashimoto’s disease, is a common autoimmune disease. An autoimmune disease is a condition that causes the body’s immune system to attack its own healthy cells.

Hashimoto’s thyroiditis is named after Kakaru Hashimoto², the first physician to describe this disease. “Thyroiditis” is a term that means “inflammation of the thyroid.” Hashimoto’s thyroiditis specifically refers to the condition that causes the immune system to attack the thyroid gland.

The thyroid is a small, butterfly-shaped gland at the base of the neck that produces hormones. These hormones regulate numerous body functions, including heart rate, blood pressure, body temperature, and weight.

When damaged, the thyroid cannot make enough thyroid hormones³. Without enough of these hormones, many of your body’s functions slow down.

Inflammation caused by Hashimoto's thyroiditis, which is referred to as chronic lymphocytic thyroiditis, often leads to an underactive thyroid gland (hypothyroidism).

Your provider can test your thyroid function to help detect Hashimoto's thyroiditis. Hashimoto's thyroiditis is relatively easy to treat and monitor on a long term basis. The most common treatment of Hashimoto’s thyroiditis is through thyroid hormone replacement.

How common is Hashimoto’s thyroiditis?

Hashimoto's thyroiditis is the most common cause of hypothyroidism. The disease affects about five people out of 100⁴ in the United States.

Hashimoto’s thyroiditis is also 5 to 10 times more common⁵ in women than men. The disease sometimes occurs in teens and young women, but it more often appears between the ages of 45 and 65. Your chance of developing Hashimoto’s thyroiditis increases if other family members have the disease.

Hashimoto’s thyroiditis causes

Researchers aren’t sure what causes⁶ some people to develop autoimmune disorders like Hashimoto’s thyroiditis. These disorders likely result from a combination of genetic tendencies and environmental factors, such as viral or bacterial infections.

Factors such as heredity, biological sex, and age all play a role in your likelihood of developing the disorder.

In people with Hashimoto’s thyroiditis, the immune system produces antibodies that attack the thyroid gland. This causes large numbers of white blood cells (called lymphocytes) to build up in the thyroid. Lymphocytes, in turn, produce the antibodies that begin the autoimmune process.

Risk factors for Hashimoto’s

Some risk factors⁷ may increase your risk of developing Hashimoto's thyroiditis:

• Biological sex: Women are much more likely to get Hashimoto's thyroiditis than men.
• Age: Hashimoto's thyroiditis can occur at any age, but most commonly occurs during middle age (between 45–65).
• Heredity: You're at higher risk for Hashimoto's thyroiditis if other members of your family have thyroid conditions or autoimmune diseases.
• Other autoimmune diseases: Having another autoimmune disease, such as rheumatoid arthritis, type 1 diabetes, or lupus, increases your risk of developing Hashimoto's thyroiditis.
• Radiation exposure: The thyroid gland is known to be vulnerable to radiation.⁸ People exposed to high levels of environmental radiation are more prone to develop Hashimoto's thyroiditis.

Hashimoto’s thyroiditis symptoms

The symptoms⁹ of Hashimoto's thyroiditis may not be easily noticeable at first. The disease typically progresses slowly over a period of years.

Hashimoto’s thyroiditis causes the thyroid to grow larger, which can cause the front of the neck to look swollen. This may be the first sign that you could have the disease.

Hashimoto’s thyroiditis also causes chronic thyroid damage, leading to a drop in the level of thyroid hormone in your blood. The symptoms of the disease are mainly those caused by an underactive thyroid gland (hypothyroidism).

Some signs and symptoms of Hashimoto’s thyroiditis include:

• Tiredness and sluggishness
• Increased sensitivity to cold
• Unexplained weight gain
• Pale, dry skin
• A puffy face
• Brittle nails
• Hair loss
• Enlargement of the tongue
• Joint and muscle pain
• Muscle weakness
• Constipation
• Excessive or prolonged menstrual bleeding
• Depression
• Memory lapses
• A feeling of fullness in your throat
• A slowed heart rate

It’s best to see your healthcare provider if you develop these signs and symptoms:

• Exhaustion without any apparent cause
• Dry skin
• Pale, puffy face
• Constipation

If you’ve taken anti-thyroid medications or have had thyroid surgery, radiation therapy, or treatment with radioactive iodine, you'll need to see your provider regularly to test how well your thyroid is functioning.

Schedule follow-up visits as often as your provider recommends if you’re undergoing hormone therapy for hypothyroidism. The dose of medications you need to properly replace your thyroid function may change over time, so your healthcare provider will need to monitor your health to determine the right dosage.

Thyroid hormones control the body’s metabolism, including cholesterol levels.¹⁰ Talk to your provider if you have high blood cholesterol, since low thyroid hormone levels may be a cause.

If left untreated, hypothyroidism caused by Hashimoto's thyroiditis can lead to a number of health complications¹¹, including:

• Goiter: The thyroid can become enlarged (called a goiter) if it receives constant stimulation for not releasing enough thyroid hormones.

Hypothyroidism is a common cause of goiter. While goiters are usually harmless, they can interfere with breathing or swallowing and affect your appearance.

• Heart problems: Hashimoto's thyroiditis may be associated with an increased risk of heart disease. Most notably, people with hypothyroidism may have high levels of low-density lipoprotein cholesterol ("bad" cholesterol). If left untreated, hypothyroidism can also lead to an enlarged heart and possibly heart failure.
• Mental health issues: Depression may occur in the early stages of Hashimoto's thyroiditis and may become more severe over time. Hashimoto's thyroiditis can also lead to slowed mental functioning and decreased sexual desire (libido) in both men and women.
• Myxedema¹²: This rare but life-threatening condition can develop due to severe hypothyroidism caused by untreated Hashimoto's thyroiditis. Signs of myxedema include drowsiness, lethargy, disorientation, stomach pain, trouble breathing, and unconsciousness.

Stress on your body, infection, exposure to cold, and sedatives might trigger myxedema coma. Myxedema requires urgent medical treatment.

• Birth defects: Thyroid hormones are crucial to the normal development¹³ of your baby’s brain and nervous systems. If you are a mother with untreated hypothyroidism from Hashimoto's thyroiditis, your baby may have a higher risk of birth defects.

Hyperthyroidism occurs in 2 to 3 out of every 100 pregnancies. You can still have a healthy pregnancy despite having a thyroid problem. You can protect your baby’s health by having regular thyroid function tests and taking all prescribed medications as directed.