Thyroid cancer in children and adolescents has to be considered as the most severe health consequence of a
nuclear reactor emergency with release of radioiodine into the atmosphere. High doses of
potassium iodide are effective to block radioiodine thyroid uptake and to prevent development of
thyroid cancer years later. However, there are controversies concerning
thyroid cancer risk induced by radioiodine exposure in adults. Further, the interaction of nutritional supply of
potassium iodide and radioiodine uptake as well as the interaction of radioiodine with certain drugs has not been addressed properly in existing guidelines and recommendations. How to proceed in case of repeated release of radioiodine is an open, very important question which came up again recently during the Fukushima accident. Lastly, the side effects of
iodine thyroid blocking and alternatives of this procedure have not been addressed systematically up to now in guidelines and recommendations. These questions can be answered as follows: in adults, the risk to develop
thyroid cancer is negligible. In countries, where nutritional
iodine deficiency is still an issue, the risk to develop
thyroid cancer after a
nuclear reactor emergency has to be considered higher because the thyroid takes up more radioiodine as in the replete condition. Similarly, in patients suffering from
thyrotoxicosis,
hypothyroidism or endemic goitre not being adequately treated radioiodine uptake is higher than in healthy people. In case of repeated or continued radioiodine release, more than one dose of
potassium iodide may be necessary and be taken up to 1 week. Repeated
iodine thyroid blocking obviously is not harmful. Side effects of
iodine thyroid blocking should not be overestimated; there is little evidence for adverse effects in adults. Newborns and babies, however, may be more sensitive to side effects. In the rare case of
iodine hypersensitivity,
potassium perchlorate may be applied as an alternative to
iodine for thyroid blocking.