Thyroiditis is a generic term for inflammation of the thyroid. Hashimoto’s thyroiditis is an autoimmune problem (your body’s immune system attacking the thyroid). It is the most common cause of hypothyroidism. De Quervain's thyroiditis is notable for fever and pain in the thyroid. It can cause hyperthyroidism and luckily goes away after several weeks. It can be treated with nonsteroidal anti-inflammatory drugs and sometimes steroids.