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Case Eleven - Toxic Multinodular Goiter

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Clinical History: 72 year old woman with symptoms of hyperthyroidism. Has complaints of recent 40 lb. weight loss, heat sensitivity, hoarseness of voice, nervousness and heart palpitations. Physical exam reveals a gland without focal nodules.

Findings: I-123 24 hour uptake and scan was performed. 24 hr uptake of the radiopharmaceutical was 53% (nl = 8-30%). Images revealed a gland of normal size with multiple focal regions of decreased activity in both thyroid lobes. Patient subsequently underwent I-131 therapy without complications.

Diagnosis: Toxic multinodular goiter.

Discussion: Hyperfunctioning thyroid nodules are the second most common cause of hyperthyroidism behind Grave’s disease. Onset of thyrotoxicosis is gradual and usually after 50 years of age. Thyroid scans may reveal hyperfunctioning nodules with the remainder of the gland showing minimal or no uptake.

Patients with this disease will lack the skin, eye, and immunologic changes which may accompany Grave’s disease. The nodules may be palpable and the gland often enlarged.

Treatment of this entity is with I-131 therapy. I-131 dose calculation may be made by:

        wt of gland (estimate) x 100 uCi of  I-131/g.
                  % uptake at 24 hrs x 10
Antithyroid drugs will not work because this entity does not undergo spontaneous remission. I-131 ablation therapy works by destroying the hyperfunctioning nodules, but spares the remainder of the gland. Thus hypothyroidism may be avoided as a side effect of therapy.

Nodules of the toxic variety may be more resistant to I-131 therapy and thus may need large doses to be effective. Recommended dosage is 20-70 mCi and may need to be repeated if symptoms persist.

References:

  1. Hinkin RE. Nuclear Medicine. Mosby 1996.
  2. Johnson JL, Felicetta JV: Hyperthyroidism: A Comprehensive Review,
    J. Am Acad Nurse Pract 1992;4(1):8-14.
  3. Houston MS, Hay ID: Practical Management of Hyperthyroidism;
    Am Fam Phys. 1990; 41(3):909-916.

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Submitted by:
Ross J. Bellavia, M.D.
Peter Faulhaber, M.D.