Around 1% to 2% of Americans suffer from Hashimoto's thyroiditis, the most common form of thyroiditis. There are also other types of thyroiditis, but they are less common. Known as chronic lymphocytic thyroiditis, Hashimoto's thyroiditis is an autoimmune condition caused by antithyroid antibodies. In addition to being the most common form of thyroiditis, it is also one of the most common causes of hypothyroidism. An autoimmune condition known as silent thyroiditis or painless thyroiditis is caused by antibodies that attack the thyroid gland. One year after giving birth, postpartum thyroiditis can result from antithyroid antibodies. This is a relatively rare occurrence. When radioactive iodine is used to treat hyperthyroidism or radiation therapy is used to treat certain cancers, radiation-induced thyroiditis occurs in some cases. De Quervain's thyroiditis, or subacute thyroiditis, is a painful condition thought to be caused by viruses. Infections of the upper respiratory tract usually precede it. Bacteria or infectious organisms cause acute infectious thyroiditis, a rare disease. A condition known as drug-induced thyroiditis occurs when medications such as amiodarone, interferons, lithium, or cytokines are used. The disease only affects a small number of people who take these drugs. There is a rare disease called Riedel thyroiditis that causes chronic inflammation and fibrosis of the thyroid gland. The process of fibrosis involves the thickening or scarring of tissues.