IS Case 223: Toxic Adenoma with complete background suppression

Nate Johnson, MD

Imaging Sciences URMC 2008
Publication Date: 2009-05-22

History

Patient is a 26-year-old female presenting with gradual onset of symptoms of hyperthyroidism over the past year. Clinical concern for Graves Disease vs toxic nodule as etiology

Diagnosis

Toxic Adenoma with complete background suppression

Discussion

When a patient presents with hyperthyroidism in the United States there is nearly a 90% chance that the etiology is due to one of these four disease states in descending order of prevalence:

  1. Graves Disease (greater than 50%)\
  2. Toxic Multinodular Goiter (15-20%)
  3. Subacute Thyroiditis (15-20%)
  4. Toxic adenoma (3-5%)

Characteristics of toxic adenoma include:

  1. Decreased TSH
  2. Radioactive iodine uptake scan with single hyperfunctioning nodule with suppressed background.
  • Contrasted with Graves which demonstrates diffusely increased uptake and toxic multinodular goiter with numerous hyperfunctioning nodules.

In our patient the background was significantly suppressed that the left lobe of the thyroid was not visualized. One must ask the patient if there is any history of thyroid surgery since removal of the left lobe could have this appearance. A congenitally missing left lobe is another possibility. The CT scan demonstrates a present left lobe of the thyroid which further supports the diagnosis of toxic adenoma with suppression of the normal background tissue.

References

  1. Thrall JH, Ziessman HA. Nuclear Medicine: The Requisites, 2nd ed., C.V. Mosby, 2001.
  2. Morton KA, Clark PB, Christensen DR, O'Malley JP. Diagnostic Imaging: Nuclear Medicine. Amirsys, 2007

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