What is Hashimoto’s Disease? Hashimoto’s disease is an autoimmune disorder that affects about 5 in 100 people in the United States, according to the Cleveland Clinic. Your immune system mistakes your thyroid for an invader and attacks it, resulting in hypothyroidism. Your thyroid is a gland in your neck that produces thyroid hormones to regulate the speed of your metabolism. Because your thyroid is essentially under attack, it cannot produce enough of the thyroid hormone known as thyroxine. Other names …