Thyroiditis: (a) Subacute thyroiditis: Subacute thyroiditis is more common in clinical practice and presents with enlarged and painful thyroid gland, fever, and hyperthyroid symptoms. Blood thyroid hormone is increased and thyrotropin is decreased. It is sometimes confused with hyperthyroidism. In subthyroiditis, thyroid 131 iodine uptake is significantly lower and thyroid nuclear imaging is significantly sparse. This is in contrast to hyperthyroidism. Painless subthyroiditis is more likely to be confused with hyperthyroidism, and the rate of 131 iodine uptake and nuclear imaging of the thyroid gland are important diagnostic factors. This disease should be considered in clinical encounters with acute enlargement of the thyroid gland with pain, fever, and increased thyroid hormones. Sometimes we encounter initial hyperthyroidism with mild disease and mildly elevated thyroid hormone levels, and painless subthyroiditis should be considered. A thyroid uptake rate of 131 iodine and/or thyroid imaging should be done to clarify the presence of subthyroiditis. Before treatment of hyperthyroidism with 131 iodine, routine thyroid 131 iodine uptake rate and nuclear imaging should be performed to further differentiate between hyperthyroidism and metritis. Sometimes hyperthyroidism and thyroiditis appear interchangeably, such as in the course of hyperthyroidism, thyroiditis appears and is clinically confused with hyperthyroidism, so it is also important to do this test. After 2 to 4 weeks of treatment of subthyroiditis, the blood thyroid hormone returns to normal, which means that the inflammation is in remission and the medication can be reduced or stopped. The recovery of thyroid imaging is slow and it is not advisable to reduce the medication according to the image, otherwise it will prolong the treatment time. (b) Hashimoto’s thyroiditis: The thyroid function in Hashimoto’s thyroiditis can be normal or hypothyroid, and the nuclear imaging can be normal or diffusely sparse. Nuclear imaging also allows observation of the degree and extent of thyroid invasion by inflammation. ( C) Acute thyroiditis: Acute thyroiditis often has a history of trauma to the thyroid gland, with acute infectious inflammatory manifestations, and generally does not require nuclide imaging.