Q: What is Wolff-Chaikoff effect?
Normal human continues to have a wide variation in dietary iodine intake and is normally autoregulated (called organification) by thyroid follicular cells. When the thyroid gland suddenly gets exposed to excess of iodine, it stops the biosynthesis of thyroid hormones, irrespective of Thyroid Stimulating Hormone (TSH). This phenomenon is called the Wolff-Chaikoff effect.
The above principle remains the mainstay of treatment in hyperthyroidism particularly in thyroid storm. Large infusion of iodine suppresses the thyroid gland. Similarly, patients who are on iodine-containing drugs such as amiodarone become hypothyroid under the same effect.
1. Wolff J, Chaikoff IL (1948). "Plasma inorganic iodide as a homeostatic regulator of thyroid function". J Biol Chem. 174 (2): 555–564. doi:10.1016/S0021-9258(18)57335-X. PMID 18865621. Link: https://www.jbc.org/article/S0021-9258%2818%2957335-X/pdf
2. Markou K, Georgopoulos N, Kyriazopoulou V, Vagenakis AG. Iodine-Induced hypothyroidism. Thyroid. 2001 May;11(5):501-10. doi: 10.1089/105072501300176462. PMID: 11396709.