[Silent thyroiditis and subacute thyroiditis]

Silent thyroiditis and subacute thyroiditis are important causes of transient thyrotoxicosis from rapidly progressive tissue injury, followed by the release of thyroid hormone into the circulation. The most striking differences between them are severe pain and extreme tenderness in the thyroid region. Although the etiology of these diseases is not clarified, silent thyroiditis is basically occurred in autoimmune thyroiditis. The most difficult differential diagnosis of silent thyroiditis is Graves' disease. TSH receptor antibody (TRAb) is useful, but TRAb is rarely positive in silent thyroiditis. A low thyroid radioiodine uptake value is most useful in identified silent thyroiditis.