The most common cause of thyroiditis is called Hashimoto's thyroiditis. This form of thyroid disease may also be referred to as chronic lymphocytic thyroiditis. As we have already discussed, this autoimmune form of thyroiditis may run in families. Additionally, families that suffer from non-thyroid autoimmune disease such as Type 1 diabetes or rheumatoid arthritis may also be at risk for the development of Hashimoto's thyroiditis.
Most patients with Hashimoto's thyroiditis don't even realize they have any thyroid disease because the symptoms are initially very mild. Most often the thyroid enlarges slightly so that it appears bulky and larger. This enlargement is due to the inflammatory cells which destroy the thyroid, resulting in long term scarring. When the cells are damaged they cease thyroid hormone production, resulting in hypothyroidism. Again the symptoms are usually mild, e.g. fatigue, difficulty concentrating and weight gain. But they can progress and become quite severe, affecting every organ system in the body as described in the section on hypothyroidism.
Occasionally, if you have Hashimoto's' thyroiditis, you may develop an overactive thyroid (hyperthyroidism), rather than the usual hypothyroidism. Too much thyroid hormone is the result of thyroid hormone release into the blood stream as thyroid cells are destroyed. This hyperthyroid period is generally short, and is followed by a period of time when the thyroid functions properly. Sometimes, however, this period of normal thyroid function is short-lived and as scarring sets in, hypothyroidism results.
The diagnosis of Hashimoto's thyroiditis is simply diagnosed by two blood tests. First the routine thyroid function tests to confirm that a patient has an underactive thyroid gland, and second the thyroid antibody tests (anti-microsomal or anti-thyroglobulin antibodies), which pinpoint Hashimoto's thyroiditis as the cause of the hypothyroidism. Anti-microsomal and anti-thyroglobulin antibodies are immune components which the body produces to attack specific portions of the thyroid cells. The anti-microsomal antibody test is much more sensitive than the anti-thyroglobulin, therefore some doctors use only the former blood test. These thyroid autoantibodies blood tests are high in about 95% of patients with Hashimoto's thyroiditis.
Thyroid Inflammation vs. Thyroid Lumps
Although the thyroid gland enlarges with Hashimoto's' thyroiditis and sometimes even has exaggerated contours called bossilations, Hashimoto's thyroiditis does not form discrete nodules or lumps in the thyroid. If you have Hashimoto's thyroiditis and a thyroid lump, it must be examined completely to insure that this nodule does not represent a cancer. This examination is usually done by needle biopsy to prove whether or not the thyroid lump is benign or malignant. Although you are unlikely to develop thyroid cancer and Hashimoto's thyroiditis together, you are at increased risk for a special type of thyroid cancer called a lymphoma which can be treated and cured if discovered early. Therefore, no thyroid nodule should be ignored.