(See also Overview of the Thyroid Gland.)
Subacute thyroiditis usually begins suddenly. In this disorder, inflammation causes the thyroid gland to release excessive amounts of thyroid hormones, resulting in hyperthyroidism, almost always followed by transient hypothyroidism and finally normal thyroid function.
Subacute thyroiditis often follows a viral illness and begins with what many people call a sore throat but actually proves to be neck pain localized to the thyroid. Many people with subacute thyroiditis feel extremely tired. The thyroid gland becomes increasingly tender, and the person usually develops a low-grade fever (99 to 101° F [37 to 38º C]). The pain may shift from one side of the neck to the other, spread to the jaw and ears, and hurt more when the head is turned or when the person swallows. Subacute thyroiditis is often mistaken at first for a dental problem or a throat or ear infection.
The diagnosis of subacute thyroiditis is made based on a person's symptoms and the results of the examination and thyroid function tests. Sometimes, it may difficult to differentiate subacute thyroiditis from Graves disease, in which case doctors do a thyroid scan and uptake test. Because of the inflammation, little or no radioactivity is taken up by the thyroid gland in subacute thyroiditis while uptake is increased in Graves disease. Thyroid ultrasonography can also help diagnose subacute thyroiditis.
Most people recover completely from this type of thyroiditis. Generally the thyroiditis resolves by itself within a few months, but sometimes it comes back or, more rarely, damages enough of the thyroid gland to cause permanent hypothyroidism.
Aspirin or other nonsteroidal anti-inflammatory drugs (NSAIDs) can relieve the pain and inflammation. In severe cases, doctors may recommend corticosteroids, such as prednisone, which are gradually decreased over 6 to 8 weeks. When corticosteroids are discontinued abruptly or too early, symptoms often return in full force. When symptoms of hyperthyroidism are severe, a beta-blocker may be recommended.
If symptoms of hypothyroidism are severe or if hypothyroidism becomes permanent, synthetic thyroid hormone (levothyroxine) may be needed.