Subacute thyroiditis is also known as De Quervain’s thyroiditis or giant cell thyroiditis. It often occurs after a viral upper respiratory infection and is a common cause of anterior neck masses and thyroid pain. The infection may cause partial destruction of thyroid follicles and epithelial detachment, colloid spillage causing thyroid foreign body reaction and infiltration of polymorphonuclear leukocytes, lymphocytes and foreign body giant cells, and giant cell granulomas around the diseased follicles are characteristic. The disease is most commonly seen in women aged 30 to 40 years. Most clinical manifestations are sudden swelling, hardening, dysphagia and painful swelling of the thyroid gland with radiation to the temporal region of the affected ear. It often starts on one side of the thyroid gland and quickly expands to other parts of the gland. Patients may have fever and increased blood sedimentation. The duration of the disease is about 3 months, and thyroid function does not decrease after healing. There is a history of upper respiratory tract infection 1 to 2 weeks prior to diagnosis. In the first week after the disease, the basal metabolic rate may be slightly higher due to partial follicular destruction, but thyroid uptake of iodine VIII is significantly lower. Treatment Prednisone 5 mg 4 times a day for 1 to 2 months, with a reduction after 2 weeks; the addition of dry thyroid preparations is more effective: if there is a recurrence after discontinuation of the drug, radiation therapy is given, with longer lasting effects. Antibiotics are not effective.