Management of Toxic Multinodular Goiter

Diagnosis and Initial Assessment

The American College of Radiology recommends that a TSH of 0 with multinodular goiter indicates toxic multinodular goiter (Plummer's disease), which requires treatment to address hyperthyroidism 1, 2
A radionuclide uptake scan should be performed to confirm that the entire goiter consists of thyroid tissue and identify hyperfunctioning nodules 2, 3
Ultrasound should be compared with the radionuclide scan to identify nodules requiring biopsy 3, 1
Iodine-123 (I-123) is preferred over iodine-131 (I-131) for diagnostic scanning due to superior imaging quality 3
Laboratory assessment should include free T3 and free T4 to determine the severity of hyperthyroidism 4

The American Medical Association recommends initiating methimazole therapy to address hyperthyroidism, which is indicated for toxic multinodular goiter when surgery or radioactive iodine is not immediately appropriate 4
Methimazole will ameliorate symptoms of hyperthyroidism while preparing for definitive therapy, but monitor for potential allergic reactions including agranulocytosis, which is a risk of antithyroid drug therapy 4

The American College of Radiology suggests choosing surgery if there is a large goiter with compressive symptoms, suspicious nodules requiring histological evaluation, or a young patient with long life expectancy, and substernal extension requiring evaluation (CT scan recommended to assess extent) 2
The American Medical Association recommends choosing radioactive iodine if there is an elderly patient or significant comorbidities increasing surgical risk, patient preference to avoid surgery, smaller goiter without significant compressive symptoms, or previous neck surgery or radiation making reoperation risky 4

The American Medical Association recommends monitoring thyroid function tests every 4-6 weeks initially, then every 3-6 months for patients treated with RAI, and initiating levothyroxine if hypothyroidism develops 4, 5
The American College of Physicians recommends initiating levothyroxine replacement therapy immediately after total thyroidectomy, and monitoring calcium levels for potential hypoparathyroidism 5

The American Medical Association warns that delaying treatment of toxic multinodular goiter can lead to cardiac complications, particularly atrial fibrillation in elderly patients 4
The American College of Radiology recommends not relying solely on Doppler ultrasound to differentiate causes of thyrotoxicosis; radionuclide uptake study is preferred as it directly measures thyroid activity 2
The American Medical Association advises avoiding iodinated contrast agents before RAI therapy as they may interfere with iodine uptake 4