A 30-year-old woman with Graves disease is rendered euthyroid with carbimazole. In preparation for subtotal thyroidectomy, Lugol iodine is added for approximately 10 days before operation. What is the principal surgical benefit sought from this regimen?

• A Permanent blockade of hormone synthesis allowing omission of antithyroid drugs
• B Reduced gland vascularity and firmness, decreasing operative blood loss ✓
• C Shrinkage of the gland through apoptosis of thyroid follicular cells
• D Prevention of recurrent laryngeal nerve oedema

Explanation

Iodine given after euthyroidism is achieved with carbimazole produces the Wolff-Chaikoff effect, reducing hormone synthesis, and acutely decreases the vascularity and friability of the hyperplastic gland, making it firmer and less bloody at surgery. The effect is transient, so iodine must not be used alone or delayed once started, since escape from the Jod-Basedow-like escape phenomenon can trigger worsening thyrotoxicosis. Apoptotic shrinkage and effects on nerves are not mechanisms of iodine benefit.

Reference: Williams Textbook of Endocrinology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.