ATA's definition. Thyroiditis is a general term that refers to “inflammation of the thyroid gland”. Thyroiditis includes a group of individual disorders that all cause thyroidal inflammation and, as a result, causes many different clinical presentations. (american thyroid association's definition).
Inflammation. Thyroiditis comes in different forms ranging from the immune system's attack on the body's own thyroid to infections of the gland - either viral or bacterial. Inflammation of the thyroid is the common link.