What is the treatment for multiple thyroid nodules using Radioiodine (I-131)?

From the Guidelines

Radioiodine therapy is not the first-line treatment for multiple thyroid nodules unless they are hyperfunctioning or there is evidence of malignancy. For multiple thyroid nodules, I recommend first obtaining a complete thyroid evaluation including thyroid function tests (TSH, free T4, free T3) and a thyroid ultrasound to characterize the nodules, as suggested by the American College of Radiology 1. Any suspicious nodules based on ultrasound features should undergo fine-needle aspiration biopsy. If nodules are benign but causing compressive symptoms or cosmetic concerns, surgical management (thyroidectomy) is typically preferred over radioiodine. However, if the nodules are hyperfunctioning and causing hyperthyroidism, radioiodine therapy with I-131 at doses of 10-30 mCi may be appropriate.

The exact dose depends on gland size and degree of hyperthyroidism. Patients should avoid close contact with children and pregnant women for several days after treatment and follow radiation safety precautions as instructed. Radioiodine works by being selectively absorbed by thyroid tissue, emitting beta radiation that destroys the cells, thereby reducing nodule size and function. Post-treatment monitoring is essential as hypothyroidism commonly develops within 3-6 months, requiring thyroid hormone replacement therapy (typically levothyroxine starting at 1.6 mcg/kg/day). It's also important to note that the use of radioiodine therapy in the treatment of differentiated thyroid carcinoma is well established, and it is recommended in high-risk patients and in low-risk patients, while there is no indication in very low-risk patients 1.

In terms of diagnosis, measurement of calcitonin should be an integral part of the diagnostic evaluation of thyroid nodules, and the initial treatment of differentiated thyroid carcinoma should always be preceded by careful exploration of the neck by ultrasound to assess the status of lymph node chains 1. The initial treatment for differentiated thyroid carcinoma is total or near-total thyroidectomy whenever the diagnosis is made before surgery and the nodule is ≥1 cm, or regardless of the size if there is metastatic, multicocal or familial DTC.

Some key points to consider when evaluating multiple thyroid nodules include:

• Obtaining a complete thyroid evaluation including thyroid function tests and a thyroid ultrasound
• Performing fine-needle aspiration biopsy on suspicious nodules
• Considering surgical management for benign nodules causing compressive symptoms or cosmetic concerns
• Using radioiodine therapy with I-131 for hyperfunctioning nodules causing hyperthyroidism
• Monitoring for hypothyroidism after radioiodine therapy and initiating thyroid hormone replacement therapy as needed.

From the Research

Radioiodine and Multiple Thyroid Nodules

• Radioiodine is a treatment option for patients with multiple thyroid nodules, particularly in cases where the nodules are causing symptoms or are suspected to be malignant 2.
• The use of radioiodine is commonly used in many parts of Europe and is considered safe and effective 2.
• However, the decision to use radioiodine should be based on the individual patient's risk factors and the characteristics of the nodules, such as their size, number, and sonographic features 3, 2.

Diagnosis and Management of Multiple Thyroid Nodules

• The diagnosis and management of multiple thyroid nodules involve a combination of clinical evaluation, thyroid function tests, ultrasound, and fine-needle aspiration biopsy (FNAB) 3, 4, 5, 6.
• The initial evaluation should include measurement of serum TSH to assess thyroid function and ultrasound examination to evaluate the number, size, and sonographic features of the nodules 3, 2.
• FNAB is a useful diagnostic tool for evaluating thyroid nodules, particularly in cases where the nodules are suspected to be malignant or have indeterminate cytology 4, 5, 6.
• The management of multiple thyroid nodules depends on the individual patient's risk factors and the characteristics of the nodules, and may include simple observation, local treatments, or surgery 3, 2, 5.

Risk of Malignancy in Multiple Thyroid Nodules

• The risk of malignancy in multiple thyroid nodules is approximately 5-15% 3, 4, 5.
• The risk of malignancy is higher in nodules with suspicious sonographic features, such as solid composition, hypoechogenicity, irregular margins, and microcalcifications 3, 5.
• The use of molecular testing, such as the Bethesda Classification System, can help to better discriminate between benign and malignant nodules and guide management 5.