The Wolf-Chaikoff effect and subsequent escape from it are important in thyroid physiology. The initial Wolf-Chaikoff effect (transient inhibition of thyroid hormone synthesis with acute iodine excess) is mediated by:

• A Iodide inhibiting TSH receptor binding at the basolateral membrane
• B High intracellular iodide inhibiting thyroid peroxidase-mediated organification ✓
• C Iodide-induced apoptosis of thyrocytes reducing hormone-producing cell mass
• D Iodide directly inhibiting deiodinase activity preventing T4 to T3 conversion

Explanation

The Wolff-Chaikoff effect occurs when acutely elevated intracellular iodide concentration inhibits thyroid peroxidase (TPO)-mediated organification of iodide (incorporation of iodide into tyrosine residues of thyroglobulin). This is a protective mechanism preventing thyroid hormone overproduction. Escape occurs within 1–2 weeks when the thyroid downregulates the sodium-iodide symporter (NIS), reducing iodide uptake and restoring normal intracellular iodide levels, allowing TPO function to resume. Patients with autoimmune thyroid disease (Hashimoto's) may fail to escape, precipitating hypothyroidism from iodine loading.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

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