Résumé
During a radiological or nuclear emergency, iodine thyroid blocking is an urgent protection action to prevent or reduce the absorption of radioactive iodine by thyroid. Although potassium iodide (KI) administration is recommended by WHO guidelines for iodine prophylaxis following nuclear accidents and is also widely implemented in most national guidelines, the scientific evidence for the guidelines lacks as the guidelines are mostly based on expert opinions and recommendations. This paper introduces the development and revision of WHO guidelines for iodine thyroid blocking published in 1989 and 1999, as well as the revision methods and main recommendations of the guidelines published in 2017, which supports the use of iodine thyroid blocking during a radiological or nuclear emergency.