Hashimoto’s thyroiditis — also called Hashimoto’s disease or chronic lymphocytic thyroiditis — is an autoimmune condition in which the immune system gradually attacks the thyroid gland. Over time, the inflammation can reduce how much thyroid hormone the gland makes. It is the most common cause of an underactive thyroid (hypothyroidism).
Thyroid hormone helps set the pace for nearly every system in the body: energy, metabolism, body temperature, digestion, mood, and thinking. That is why Hashimoto’s symptoms are so wide-ranging — and why they are so often blamed on something else. The process usually develops slowly, over months or years, so many people adjust to feeling worse without realizing it.
Hashimoto’s is more common in women, often appears in middle age, and tends to run in families. People who already have another autoimmune condition may also be more likely to develop it.
This page covers the symptoms. For how we test for and treat Hashimoto’s, see our Thyroid & Hashimoto’s care page.