The disease overlaps in occurrence with other autoimmune diseases, including pernicious anemia, myasthenia gravis, Addison's disease, and premature ovarian failure, as well as with diabetes mellitus. The existence of any of these conditions except diabetes should enhance suspicion of thyroid disease. The course of Hashimoto's thyroiditis is extremely variable. Diagnostic approaches include careful palpation of the neck and measurement of antibody, TSH, and T 4 levels. Thyroid needle biopsy is occasionally useful when the gland appears irregular and hard enough to suggest malignant disease.
Treatment is straightforward.
Thyroxine is used to suppress the goiter or to correct hypothyroidism. In some patients, thyrotropin receptor-blocking antibodies, presumably implicated in the hypothyroidism, disappear. When thyroxine replacement is discontinued in these patients, they remain euthyroid. This disorder has been reported frequently enough so that the RAIU, the only test that can detect it, should be reinstated in the routine workup of hyperthyroid patients. It can produce hyperthyroidism, hypothyroidism, or first one disorder and then the other.