Thyroid blocking

Administration of a compound of stable iodine (usually potassium iodide) to prevent or reduce the unwanted uptake of radioactive isotopes of iodine by the thyroid in the event of an accident involving radioactive iodine or in patients administered radioiodine containing radiopharmaceuticals where there is the potential for the presence of unbound or “free” iodine (e.g. 123I or 131I).

ICRP Glossary entry - May 2019