Thyroiditis is a group of diseases characterized by inflammation of the thyroid gland. There are several types of thyroiditis, the causes of which are not the same for different types, but are not contagious. Common classifications and causes of thyroiditis include: thyroiditis can be divided into 3 types according to the course of the disease: acute, subacute and chronic. Acute thyroiditis: according to the etiology it can be subdivided into; viral thyroiditis, caused by viral infection; bacterial, purulent thyroiditis, with clinical manifestations of fever, pressure pain, painful swallowing, enlargement of the thyroid gland, mostly on one side, and signs of infection of adjacent organs and tissues. Acute thyroiditis is a rare or uncommon inflammation of the thyroid gland, mainly in children, mostly due to abnormal development of the thyroid gland or with other abnormalities of the neck and later secondary bacterial infection, such as abnormal development of the cheek cleft. It may be acute, with high fever and purulent inflammatory changes, but the nail function is usually normal. This type is a foreign bacterial infection and the infectiousness depends on the causative bacteria. Subacute thyroiditis: Also known as granulomatous thyroiditis and cytomegalic thyroiditis, this is a self-limiting thyroiditis associated with viral infections such as influenza virus, coxsackie virus, adenovirus, and mumps virus. These viruses are infectious, but their ability to cause disease is also related to autoimmune status, and thyroiditis does not necessarily occur with viral infections. Clinical manifestations include neck pain with fever, acute onset, initial upper whistle infection, and disappearance of antibodies to the virus as the condition improves. Painless thyroiditis: the infiltration of lymphocytes in the thyroid gland is mild and only focal, manifesting as transient reversible destruction of the thyroid follicles. In half of the patients, the thyroid gland is mildly enlarged, diffuse, hard in texture, and without local tenderness. The thyrotoxicosis of this disease is due to the destruction of thyroid follicles by inflammation and leakage of thyroid hormones into the circulation. Postpartum thyroiditis is also a variant of painless thyroiditis. This type is also associated with an autoimmune condition, but is not contagious. Autoimmune thyroiditis: A major type of thyroiditis associated with an autoimmune response, they are characterized by the presence of serum antibodies against the thyroid itself and the presence of infiltrating lymphocytes in the thyroid, but the degree of thyroid destruction is not necessarily proportional to the symptoms of hypothyroidism. Common types of diseases include: Hashimoto’s thyroiditis, atrophic thyroiditis, quiet thyroiditis, postpartum thyroiditis, medication thyroiditis, and Hashimoto’s thyrotoxicosis. The main cause of this type of thyroiditis is an autoimmune reaction with some genetic component, but it is not contagious. Therefore, most types of thyroiditis are related to autoimmunity and have some genetic factors, but are not contagious; a few types depend on the type of pathogen.