Hashimoto's thyroiditis is a disorder in which the immune system mistakenly attacks healthy tissue in the thyroid gland (located at the base of the neck).
This attack causes inflammation and interferes with the thyroid gland's ability to produce hormones that control many functions in the body.
Hashimoto's thyroiditis is the most common cause of hypothyroidism (underactive thyroid) in the United States.
The disease is also known as chronic lymphocytic thyroiditis or autoimmune thyroiditis.
It's named after the Japanese surgeon who first discovered it in 1912.
Not everyone with Hashimoto's thyroiditis develops hypothyroidism.
You develop hypothyroidism when your thyroid gland can no longer make enough of its hormones.
People with Hashimoto's thyroiditis who do have hypothyroidism may experience mild symptoms, or no symptoms at all — especially at first.
As the disease progresses, you may begin to experience signs of hypothyroidism.
Hashimoto's Thyroiditis Prevalence
Hashimoto's thyroiditis affects about 1 to 2 percent of people in the United States, according to the National Institutes of Health.
The disease is more common in women than in men.
It can occur at any age, but is more likely to affect people between ages 30 and 50.
Causes and Risk Factors
Doctors don't know exactly what causes Hashimoto's thyroiditis.
The following factors may increase your risk of developing the disease:
Gender: Women are seven times more likely than men to develop Hashimoto's thyroiditis.
Age: The disease is diagnosed most often in middle-aged adults.
Genes: You have a higher risk of developing the condition if other members of your family have thyroid or autoimmune diseases.
Hashimoto's Thyroiditis and Pregnancy
In pregnant women, hypothyroidism is typically caused by Hashimoto's thyroiditis and occurs in 3 to 5 of every 1,000 pregnancies, according to the National Institutes of Health.
If hypothyroidism isn't treated during pregnancy, it can lead to miscarriage, premature birth, stillbirth, other congenital issues, or preeclampsia (high blood pressure during pregnancy).
Thyroid medications used to correct the problem are usually safe to take during pregnancy.
If you have Hashimoto's thyroiditis, tell your doctor if you're pregnant or plan to become pregnant.
Hashimoto's Thyroiditis Complications
If it's not treated, Hashimoto's thyroiditis can cause complications, including:
Goiter (enlarged thyroid): Hashimoto's thyroiditis can cause a large goiter to grow, which may affect your appearance.
Goiters sometimes interfere with swallowing or breathing.
Mental health issues: The condition raises your risk of depression and may slow your mental function.
Birth defects: Babies born to mothers with Hashimoto's thyroiditis have a higher risk of birth defects.
Myxedema (severe hypothyroidism): People with Hashimoto's thyroiditis sometimes develop this rare, life-threatening form of hypothyroidism.
- Hashimoto's disease: Mayo Clinic.
- Hashimoto thyroiditis: Genetics Home Reference.
- Hashimoto's Disease: National Institute of Diabetes and Digestive and Kidney Diseases.
- Hypothyroidism (underactive thyroid): Mayo Clinic.
Last Updated: 12/22/2015