What is thyroiditis?
Thyroiditis is an inflammation on the thyroid gland and the most common cause of hypothyroidism. When patients with thyroiditis have any symptoms, they are usually the symptoms of hypothyroidism. It’s also common to have an enlarged thyroid that may shrink over time. The type of thyroiditis seen most often is Hashimoto’s thyroiditis, a painless disease of the immune system that runs in families. Hashimoto's thyroiditis affects about 5% if the adult population, increasing particularly in women as they age.
The thyroid is the largest gland in the neck. It produces, secretes, and stores thyroxine (T4), a hormone that influences the metabolism of just about every body process. When the thyroid gland is functioning properly, hormone release is carefully regulated. When bacteria or viruses invade and inflame the gland, T4 surges into the bloodstream and raises hormone levels that then discourage the gland from creating more T4. Eventually the hormone stores are exhausted, the thyroid loses its ability to manufacture T4, and an underactive thyroid (hypothyroidism) results. This condition is more common in women than in men and usually develops between ages 30-50.
The thyroid gland usually contains an abundance of thyroid hormone that is stored in follicles and released when needed. Inflammation of the thyroid, termed thyroiditis, may result in uncontrolled release of thyroid hormone from the inflamed gland, leading to hyperthyroidism. The inflammation may be silent and non-painful, and patients may be unaware that the thyroid gland is affected by the inflammatory process. Thyroiditis also commonly occurs after pregnancy, and hence may be referred to in this instance as ‘postpartum thyroiditis’.
Alternatively, thyroid inflammation may be quite severe and painful (subacute thyroiditis), producing local neck discomfort, neck tenderness, difficulty with swallowing and symptoms of systemic inflammation, including fatigue, fever, loss of appetite and weight loss. With both types of thyroiditis, the inflammation can produce some degree of thyroid enlargement, which can be particularly prominent with subacute thyroiditis.
If enough thyroid hormone is released from the inflamed thyroid gland, mild to severe hyperthyroidism may develop, that can last for weeks to months. Following the resolution of thyroiditis, the thyroid gland often begins to function normally again, and no further treatment may be necessary. If the inflammation has produced significant permanent damage to the thyroid, the gland may not be able to function normally after the inflammation has subsided, and hypothyroidism may ensue.
What is Hashimoto's thyroiditis?
Thyroiditis, or inflammation of the thyroid gland, has many causes. The most common cause is Hashimoto's thyroiditis. This is a chronic inflammatory disorder of the thyroid gland caused by abnormal blood antibodies and white blood cells attacking and damaging thyroid cells. The end result of this so-called "autoimmune" destruction is hypothyroidism caused by the complete absence of thyroid cells. However, in many patients, sufficient thyroid reserve remains to prevent hypothyroidism.
Hashimoto's thyroiditis is most common among women, particularly older women, and tends to run in families. The condition occurs more frequently among people with certain chromosomal abnormalities, including Down, Turner's, and Klinefelter's syndromes. Hashimoto's hyroiditis often begins with a painless, firm enlargement of the thyroid gland or a feeling of fullness in the neck. The gland usually has a rubbery texture and sometimes feels lumpy. In about 50% of people with Hashimoto's thyroiditis, the thyroid becomes underactive. In most of the rest, the thyroid remains normal. In a small number of people, the gland initially becomes overactive, after which it usually becomes underactive.
Doctors perform thyroid function tests on blood samples to determine whether the gland is functioning normally; however, the diagnosis is based on a physical examination and the results of a blood test to determine whether the person has antithyroid antibodies, which attack the thyroid gland. The level of thyroid-stimulating hormone (TSH) is measured to be sure that hypothyroidism is not present. Most people eventually develop hypothyroidism and then must take thyroid hormone replacement therapy for the rest of their lives. Thyroid hormone may also be useful in reducing the size of the enlarged thyroid gland. People with Hashimoto's thyroiditis should avoid excess iodine (which can cause hypothyroidism) from natural sources, such as kelp tablets and seaweed.
Hashimoto's disease slowly destroys thyroid tissue and robs the gland of its ability to change iodine into T4. The condition progresses so gradually that many people who have it do not realize anything is wrong until the enlarged gland forms a goiter, a swelling seen and felt in the front of the neck. This may not happen until weeks or even years after an individual develops Hashimoto's. |
