What is subacute thyroiditis?
Subacute thyroiditis is a disease in which inflammation of the thyroid gland is accompanied by fever and pain in the thyroid. “Subacute” symptoms last longer than “acute” symptoms, but they are not chronic. Subacute thyroiditis occurs more often in women than men. It most commonly afflicts women in their 30s and 40s.
Cause
The cause of subacute thyroiditis has not been identified. It often occurs with persistent cold-like symptoms, suggesting that viruses may be involved. However, no definitive conclusion has been reached.
Symptoms
The symptoms of subacute thyroiditis are temporary. They appear when inflammation is severe but resolve naturally.
(1) Symptoms due to inflammation:
• Thyroid pain The degree of pain varies, ranging from mild pain when swallowing or touching the thyroid area to severe pain that spreads to the ears and chest even when at rest.
• Thyroid swelling The entire thyroid or only a portion (the left or right side) swells and becomes rigid. A characteristic of this condition is for the location of swelling and pain to shift with time, such as from the left to the right side.
• Fever Fevers range from low to high. In some cases, fever may not be clearly present.
(2) Symptoms due to abnormal thyroid hormones levels
Thyroid inflammation leads to the destruction of follicular cells that produce thyroid hormones. This causes hormones stored in the thyroid gland to be released into the bloodstream. As a result, hormone levels in the blood rise. Symptoms appear that are similar to those found in Basedow’s disease, such as heart palpitations and shortness of breath. After a period of high thyroid hormone levels passes, hormone levels temporarily drop, and then gradually return to normal.
Examinations
The following examinations are used for diagnosis:
(1) Blood tests • A raised level of C-reactive protein (CRP) is an indicator of inflammation. • Since thyroid cells are destroyed, thyroid hormone and thyroglobulin levels in the bloodstream increase.
(2) Ultrasonography • Thyroid swelling and changes due to inflammation can be detected.
(3) Isotope (radioactive iodine) uptake test • This test is performed when it is necessary to distinguish subacute thyroiditis from other diseases that cause increased thyroid hormone levels.
Treatment
During treatment for subacute thyroiditis, please avoid exercise and try to rest as much as possible. The condition resolves naturally in mild cases. However, medications are provided to treat symptoms if there is fever, severe pain, or tachycardia caused by high hormone levels.
• Fever and pain Corticosteroids (steroid medications) or non-steroidal anti-inflammatory drugs are selected depending on the severity of fever or pain. The dosage of corticosteroids is reduced gradually according to the symptoms over 2-3 months. Until instructions to conclude medication are given, please seek care before a prescription finishes. Please do not make sudden decisions based on your own judgement.
• Tachycardia If tachycardia is present, medication to control heartrate may be co-administered.
Outcome
For most people, symptoms disappear in 2-3 months and thyroid hormone levels return to normal. However, in a portion of cases, thyroid function remains low, necessitating thyroid hormone medication. Relapse is rare, but acute thyroiditis may reemerge after 10 or more years have passed.