Wolff–Chaikoff effect

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The Wolff–Chaikoff effect (pronounced "woolf' cha'kof"),[1] discovered by Drs. Jan Wolff and Israel Lyon Chaikoff at the University of California, is a reduction in thyroid hormone levels caused by ingestion of a large amount of iodine.[2] In 1948, Wolff and Chaikoff reported that injection of iodine in rats almost completely inhibited organification (oxidation of iodide) in the thyroid gland.[3][4] Patients with Graves' disease are more sensitive than euthyroid patients,[5] and iodine has been used to manage Graves' disease.

The Wolff–Chaikoff effect is an autoregulatory phenomenon that inhibits organification in the thyroid gland, the formation of thyroid hormones inside the thyroid follicle, and the release of thyroid hormones into the bloodstream.[6] This becomes evident secondary to elevated levels of circulating iodide. The Wolff - Chaikoff effect is an effective means of rejecting a large quantity of imbibed iodide, and therefore preventing the thyroid from synthesizing large quantities of thyroid hormone.[7] The Wolff–Chaikoff effect lasts several days (around 10 days), after which it is followed by an "escape phenomenon",[8] which is described by resumption of normal organification of iodine and normal thyroid peroxidase function. "Escape phenomenon" is believed to occur because of decreased inorganic iodine concentration secondary to down-regulation of sodium-iodide symporter (NIS) on the basolateral membrane of the thyroid follicular cell.

The Wolff–Chaikoff effect can be used as a treatment principle against hyperthyroidism (especially thyroid storm) by infusion of a large amount of iodine to suppress the thyroid gland. Iodide was used to treat hyperthyroidism before antithyroid drugs such as propylthiouracil and methimazole were developed. Hyperthyroid subjects given iodide may experience a decrease in basal metabolic rate that is comparable to that seen after thyroidectomy.[6] The Wolff–Chaikoff effect also explains the hypothyroidism produced in some patients by several iodine-containing drugs, including amiodarone. The Wolff–Chaikoff effect is also part of the mechanism for the use of potassium iodide in nuclear emergencies.[9][10][11]

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References[edit]

  1. ^ Dorland (2011). Dorland's Illustrated Medical Dictionary. Elsevier Health Sciences. p. 2083. ISBN 9781416062578. 
  2. ^ Physiology at MCG 5/5ch5/s5ch5_6
  3. ^ Panneels, V.; Juvenal, G.; Boeynaems, J.M.; Durmont, J.E.; Sande, J. Van (2009). "Iodide Effects on the Thyroid: Biochemical, Physiological, Pharmacological, and Clinical Effects of Iodide in the Thyroid". In Preedy, Victor R.; Burrow, Gerard N.; Watson, Ronald Ross. Comprehensive Handbook of Iodine: Nutritional, Biochemical, Pathological and Therapeutic Aspects. Academic Press. p. 304. ISBN 9780080920863. 
  4. ^ Wolff J, Chaikoff IL (1948). "Plasma inorganic iodide as a homeostatic regulator of thyroid function". J Biol Chem 174 (2): 555–564. 
  5. ^ King; Tekoa, Mary Brucker (2010). Pharmacology for Women's Health. Jones & Bartlett Learning. p. 549. ISBN 9780763753290. 
  6. ^ a b Goodman, Louis Sanford; Gilman, Alfred Goodman (1996). Goodman and Gilman's the pharmacological basis of therapeutics (9th ed.). McGraw-Hill. p. 1402. ISBN 978-0-07-026266-9. 
  7. ^ Markou, K (May 2001). "Iodine induced hypothyroidism". Thyroid 11 (5): 501–10. PMID 11396709. 
  8. ^ Eng P, Cardona G, Fang S, Previti M, Alex S, Carrasco N, Chin W, Braverman L (1999). "Escape from the acute Wolff-Chaikoff effect is associated with a decrease in thyroid sodium/iodide symporter messenger ribonucleic acid and protein". Endocrinology 140 (8): 3404–10. doi:10.1210/en.140.8.3404. PMID 10433193. 
  9. ^ Sternthal E, Lipworth L, Stanley B, Abreau C, Fang SL, Braverman LE (1980). "Suppression of thyroid radioiodine uptake by various doses of stable iodide". N Engl J Med 303 (19): 1083–8. doi:10.1056/nejm198011063031903. PMID 7421914. "The effect is rapid because of rapid inhibition of intrathyroid organification of iodide (acute Wolff–Chaikoff effect) and saturation of the iodide-transport mechanism." 
  10. ^ Becker DV (1983). "Physiological basis for the use of potassium iodide as a thyroid blocking agent logistic issues in its distribution". Bull N Y Acad Med 59 (10): 1003–8. PMID 6582961. "In larger amounts [potassium iodide] acts immediately to block further uptake of iodide by several means, particularly by saturating the iodide transport mechanisms of the thyroid, by inhibiting the intrathyroidal organification of iodide, and by simple dilution." 
  11. ^ Adelstein SJ (1991). “Intervention procedures for radionuclides.” Anticarcinogenesis and Radiation Protection 2. Springer US. pp. 227-8. "'Cold' iodide is effective in four ways: (a) by diluting the entering iodide pool; (b) by saturating the iodide transport system; (c) by blocking organification of iodide and thus inhibiting thyroid hormone synthesis (the Wolff-Chaikoff effect); and (d) by promoting excretion and thus lowering the total body dose."