What is the treatment for multinodular toxic goiter disease?

Treatment for Toxic Multinodular Goiter

For toxic multinodular goiter, definitive treatment with either radioiodine therapy or total thyroidectomy is recommended, with the choice depending on goiter size, compressive symptoms, and patient factors—radioiodine is preferred for smaller glands without obstruction, while surgery is indicated for large goiters (>80-100g), compressive symptoms, or when rapid cure is needed. 1, 2, 3

Initial Medical Management

Antithyroid drugs are used for symptom control but not as definitive long-term therapy:

• Methimazole is the first-line antithyroid drug for toxic multinodular goiter to ameliorate hyperthyroid symptoms in preparation for definitive treatment with surgery or radioiodine 4
• Propylthiouracil is reserved for patients intolerant of methimazole 5
• Critical pitfall: Unlike Graves' disease, toxic multinodular goiter does not remit with antithyroid drugs—these medications only control symptoms temporarily and should not be relied upon as sole long-term therapy expecting remission 3
• However, recent evidence suggests long-term low-dose methimazole (4-6 mg daily) for 60-100 months can maintain euthyroidism in 96% of patients with minimal side effects, though this remains controversial and is not standard practice 6

Definitive Treatment Selection Algorithm

Choose between radioiodine and surgery based on these specific criteria:

Radioiodine Therapy (131-I) is preferred when:

• Thyroid volume is <80-100 grams 7, 8
• No compressive symptoms (dyspnea, dysphagia, orthopnea) are present 3, 9
• Patient refuses or has high surgical risk 7
• No substernal extension requiring imaging confirmation 1, 2

Radioiodine dosing and outcomes:

• Standard dose: 3.7 MBq/g thyroid tissue (corrected to 100% 24-hour uptake), typically 25-30 mCi for most patients 7, 8
• Single dose cures 78% of patients; 92% are cured with 1-2 treatments 7, 8
• Median thyroid volume reduction of 43% occurs by 24 months post-treatment 7
• Hypothyroidism develops in 14-41% within 5 years, requiring lifelong levothyroxine replacement 7, 6
• Euthyroidism achieved in 52% within 3 months, with 37% remaining euthyroid long-term 7, 6

Total Thyroidectomy is indicated when:

• Large goiter (>80-100 grams) where single radioiodine dose unlikely to cure 2, 9, 8
• Compressive symptoms present: dyspnea, orthopnea, dysphagia, or dysphonia 3, 9
• Substernal extension confirmed on CT imaging 1, 2
• Rapid cure needed (surgery achieves euthyroidism faster than radioiodine) 9
• Concern for malignancy based on FNA of suspicious nodules 9
• Patient preference after discussing risks/benefits 2

Surgical approach:

• Total thyroidectomy with bilateral central neck dissection if indicated 2
• Requires lifelong thyroid hormone replacement with TSH maintained in normal range (not suppressed, as toxic multinodular goiter is not TSH-dependent) 1, 2

Preoperative Workup

Before definitive treatment, complete this diagnostic sequence:

1. TSH measurement first—if suppressed, proceed with imaging 10, 3
2. Thyroid ultrasound to assess morphology, nodule characteristics, and measure gland size 1, 2, 10
3. Radioiodine uptake scan with I-123 (preferred over I-131) to confirm autonomous function and identify hypofunctioning nodules requiring FNA 1, 10
4. CT neck/chest if substernal extension or tracheal compression suspected 1, 2
5. FNA of hypofunctioning or suspicious nodules identified on ultrasound, as "hot" nodules can still harbor malignancy 10, 9

Special Considerations

If exophthalmos is present:

• This suggests coexistent Graves' disease with autoimmune component 2
• Radioiodine may worsen eye disease—surgery becomes preferred option 2
• Eye symptoms may improve after definitive treatment of thyrotoxicosis 2

For patients refusing surgery with very large glands:

• Consider laser ablation treatment (LAT) to reduce nodule volume before radioiodine as alternative strategy, though this is not standard practice 11
• Multiple radioiodine doses (up to 3-5 treatments) may be needed for massive goiters 7, 8

Monitoring after treatment:

• Regular thyroid function tests to assess for hypothyroidism or persistent hyperthyroidism 2, 7
• Ultrasound to monitor residual goiter size if radioiodine used 7
• Lifelong levothyroxine replacement after surgery or if hypothyroidism develops post-radioiodine 2, 7