Toxic Multinodular Goiter vs Graves Disease

Toxic multinodular goiter may have a similar clinical presentation as Graves disease, and a thyroid scan can help differentiate the two.

The thyroid in a patient with Graves disease (bottom image, I-123) will be enlarged and demonstrate diffusely increased uptake without focal nodules. The thyroid in a patient with toxic multinodular goiter (top image, I-123) will demonstrate heterogeneous distribution of radiotracer with or without discrete "hot" nodules. Single toxic nodules are frequently associated with decreased uptake in the remainder of the gland. Quantitative uptake may be normal or only mildly elevated in toxic multinodular goiter.

A potential source of confusion is Graves disease in a patient with a nodular thyroid gland.

References

Sarkar SD. Benign thyroid disease: what is the role of nuclear medicine? Semin Nucl Med. 2006 Jul;36(3):185-93.