Hashimoto’s Disease also knows as Hashimoto’s thyroiditis, is an autoimmune condition in which the immune system attacks and damages the thyroid gland. This disease is more frequently seen in women than men and is the leading cause of hypothyroidism, or an underactive thyroid. Hypothyroidism can be effectively managed with medication, but if left untreated, it can cause difficulties with becoming pregnant and lead to complications during pregnancy. Typical signs of hypothyroidism include tiredness, weight gain, feeling down, and joint discomfort.