Wolff-Chaikoff effect

The Wolff-Chaikoff effect is a protective response by the thyroid gland to a sudden, large increase in iodine levels. Normally, iodine is essential for making thyroid hormones, but too much iodine temporarily reduces the gland’s hormone production. This happens because excess iodine temporarily inhibits the enzyme involved in hormone synthesis, preventing overproduction. The effect helps prevent excessive thyroid hormones during brief periods of high iodine exposure, such as from certain medications or contrast dyes used in imaging. Usually, after a few days, the thyroid adapts and resumes normal hormone production despite the high iodine levels.