What is Hashimoto's disease?

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    Last Updated: May 16, 2025

    Hashimoto's disease is an autoimmune disorder in which the immune system attacks the thyroid gland, which leads to tissue damage and decreased production of thyroid hormones, resulting in hypothyroidism. It is most common in women aged 30 to 50 and is often associated with other autoimmune diseases.

    The thyroid gland is a small, butterfly-shaped gland located in the front of the neck, just under the voice box. It plays a vital role in regulating numerous body functions, including heart rate, body temperature, metabolism, and growth and development, through the production of thyroid hormones that communicate with various cells and tissues in the body.

    Hashimoto’s thyroiditis is an autoimmune disorder and the most common cause of hypothyroidism (underactive thyroid) in the U.S. and in other regions of the world with sufficient iodine intake (which is necessary for the thyroid gland to function properly). In people with Hashimoto’s disease, the immune system inappropriately targets the thyroid gland, leading to tissue damage, inflammation and scarring that ultimately decreases thyroid hormone production. The disease often appears in people who are 30-50 years old and is at least 10 times more common in women than men.[1] Hashimoto’s disease is strongly associated with other autoimmune diseases, so your physician may search for other disorders associated with autoimmunity.