What is the initial treatment for a patient with multiple nodular toxic goiter?

Initial Treatment for Toxic Multinodular Goiter

Begin with methimazole to control hyperthyroidism while preparing for definitive therapy with either radioactive iodine or surgery, with the choice between these definitive options determined by goiter size, compressive symptoms, patient age, and comorbidities. 1, 2

Immediate Medical Management

• Start methimazole at 15-20 mg daily to ameliorate hyperthyroid symptoms while preparing for definitive treatment 1, 2, 3
• Methimazole is FDA-approved specifically for toxic multinodular goiter when surgery or radioactive iodine is not immediately appropriate 2
• Do not exceed 15-20 mg/day as starting dose, since agranulocytosis risk is dose-dependent 3
• Monitor complete blood count for agranulocytosis, particularly in the first 3 months of therapy 1
• Avoid propylthiouracil as first-line agent due to risk of severe liver failure requiring transplantation 3

Diagnostic Workup During Medical Stabilization

• Obtain radionuclide uptake scan (preferably I-123) to confirm hyperfunctioning nodules and that the entire goiter consists of thyroid tissue 1
• Perform thyroid ultrasound and compare with radionuclide scan to identify any nodules requiring biopsy 1
• Measure free T3 and free T4 to determine hyperthyroidism severity 1
• If compressive symptoms or substernal extension suspected, obtain CT scan to assess extent 1

Definitive Treatment Selection Algorithm

Choose surgery (total or near-total thyroidectomy) if: 1

• Large goiter with compressive symptoms (tracheal compression, dysphagia, dyspnea)
• Suspicious nodules requiring histological evaluation
• Young patient with long life expectancy
• Substernal extension present
• Previous neck surgery or radiation making future intervention risky

Choose radioactive iodine (I-131) if: 1, 4

• Elderly patient or significant surgical comorbidities
• Patient preference to avoid surgery
• Smaller goiter without significant compressive symptoms
• No suspicious nodules requiring histological diagnosis
• Estimated goiter weight allows for effective dosing (typically 200 μCi per gram) 4

Critical Pre-Definitive Treatment Considerations

• Stop methimazole at least one week before radioactive iodine to reduce treatment failure risk 3
• Avoid iodinated contrast agents before RAI therapy as they interfere with iodine uptake 1
• For surgery, continue methimazole until euthyroid state achieved to prevent thyroid storm 1

Post-Definitive Treatment Management

After total thyroidectomy: 1

• Initiate levothyroxine replacement immediately
• Monitor calcium levels for hypoparathyroidism

After radioactive iodine: 1

• Monitor thyroid function tests every 4-6 weeks initially, then every 3-6 months
• Initiate levothyroxine when hypothyroidism develops (expected in most patients)
• Be aware that 78% achieve euthyroid state with single dose, though persistent goiter common 4

Common Pitfalls to Avoid

• Do not delay treatment, as toxic multinodular goiter can lead to atrial fibrillation and cardiac complications, particularly in elderly patients 1
• Do not rely solely on Doppler ultrasound to differentiate causes of thyrotoxicosis; radionuclide uptake study directly measures thyroid activity and is preferred 1
• Be aware that autoimmune hyperthyroidism can develop 3-10 months after radioiodine treatment for multinodular goiter, requiring continued monitoring in the first year 5
• Recognize that up to 22% of patients may require a second dose of radioactive iodine for adequate control 4