Painless thyroiditis (PT), also known as silent thyroiditis (ST), is a special type of thyroiditis. Since Hamburger first described a case called "latent subacute thyroiditis" in 1971, more and more scholars have reported such cases and recognized that it is an independent disease. ST has the common characteristics of subacute thyroiditis and chronic lymphocytic thyroiditis, but they are not exactly the same. In recent years, some people have classified it as subacute thyroiditis and called it subacute lymphocytic thyroiditis to distinguish it from subacute granulomatous thyroiditis (commonly known as subacute thyroiditis). In addition, this disease also has other names such as subacute non-suppurative thyroiditis and postpartum painless thyroiditis.