The thyroid scan in Hashimoto's thyroiditis: the great mimic.

We have reviewed our experience over the past 5 years of 32 thyroid scans in Hashimoto's thyroiditis. A wide variety of images were obtained, the most common finding being that of an enlarged gland with diffusely increased tracer uptake, a pattern identical to that found in Graves' disease (eight patients). Of the remainder, four scans were normal, four showed an enlarged gland with normal tracer uptake, five a multinodular gland with normal tracer uptake, five a multinodular gland with high tracer uptake, five a single non-functioning nodule and in one patient there was low tracer uptake by the gland. It is apparent that the thyroid scan in Hashimoto's thyroiditis can mimic a wide range of thyroid disorders. Thus, taken in isolation, the scan findings can be misleading and should be evaluated in conjunction with current biochemistry.