Thyroiditis is inflammation (not an infection) of the thyroid gland. The inflammation can be a result of a bacterial infection. It can also be caused due to a chronic condition caused by an autoimmune response. Autoimmune response is a state where the immune system fails to recognize the body’s constituents and the lymphocytes attack the thyroid gland, rather than attacking external pathogens alone.
There are several types of thyroiditis. The most common among them is Hashimoto’s thyroiditis, which is a thyroid condition where inflammation results due to an autoimmune response. Apart from that, there is postpartum thyroiditis, sub-acute (also known as De Quervain’s thyroiditis), silent thyroiditis and drug and radiation-induced thyroiditis. Each type has different causes, clinical features, diagnoses, risks and treatments.
The symptoms of thyroid, including thyroiditis, tend to mimic symptoms of other diseases, which make the condition difficult to diagnose. The most common indication of thyroiditis is tenderness and enlargement of the gland. This can be felt by an expert physician by palpating the thyroid gland externally. Blood tests, thyroid scans taken after administration of oral radioiodine, and fine needle biopsy are other means of confirming the diagnosis.
Hashimoto’s thyroiditis was first described in 1912. In this condition, the thyroid is unable to convert iodine into thyroid hormone and enlarges, usually on one side, trying to compensate its inability. Although it leads to hypothyroidism, a thyroid problem of inadequate production of hormones, the gland retains the ability to take up iodine. A thyroid supplement of synthetic or animal-based hormones, usually cures the hypothyroidism and the enlargement. As it is an autoimmune disease, the antibodies that initially attacked the gland may remain in the body for years, which may require lifelong treatment.
Sub-acute thyroiditis causes tenderness and rapid swelling of the thyroid gland, and is very painful. The gland releases thyroid hormone in the bloodstream, leading to hyperthyroidism. The thyroid in this case is unable to take up iodine. This thyroid condition is similar to an infection, but to this date, no infectious agent or antibodies have been identified. The preferred mode of treatment is bed rest and aspirin to reduce the inflammation, because the hyperthyroidism usually resolves within several weeks.
Silent thyroiditis was identified in 1970s and is usually seen in young women after pregnancy. The symptoms are similar to Graves’ disease, but on the milder side. This type of thyroiditis is somewhat midway between Hashimoto’s and sub-acute thyroiditis. The level of hormones in the blood is high (a hyper condition) and the uptake of iodine is low as in sub-acute thyroiditis. However, it is differentiated from it by the absence of pain and tests of fine needle aspirate resemble Hashimoto’s thyroiditis. The condition usually resolves on its own within three months.