Adverse effects of iodine thyroid blocking: a systematic review

Abstract

(131)I, when released in a radiological or nuclear accident as happened recently in Fukushima, Japan, may cause thyroid cancer as a long-term consequence. Iodine thyroid blocking (ITB) is known to reduce the risk of developing thyroid cancer. Potential adverse effects of ITB have not been systematically investigated so far. This article summarises the results of a review on adverse effects of ITB based on a systematic literature search in scientific medical databases. A meta-analysis was not performed as identified studies displayed major heterogeneity. The search resulted in 14 articles relevant to the topic, reporting mostly on surveys, ecological and intervention studies. Only one study from Poland focused on effects (both desired and adverse) of an ITB intervention following the Chernobyl accident. All other studies reported on iodine administration in a different context. Overall, the studies did not reveal severe adverse reactions to potassium iodide in the general public. Since ITB is a protective measure only applied in very specific circumstances, scientifically sound studies of adverse effects are scarce and consequently the evidence base is weak. The assessment of adverse effects of ITB relies on indirect evidence from related areas. This study may contribute to ongoing developments in pharmacoepidemiology aiming to better quantify adverse effects of medications and health care interventions including ITB.

The Hypothalamic-Pituitary-Thyroid Axis in Infants and Children: Protection from Radioiodines

“…Safety concerns have been expressed regarding KI administration to infants and children while also ensuring adequate protection from radioiodine exposure [59]. The effectiveness of KI to reduce systemic radioiodide uptake into the thyroid gland in a clinical environment is inferred by evaluating the reduction in fractional RAIU.…”

“…Chronic treatment with iodine for goiter has caused hyperthyroidism [59]. Hypothyroidism has also occurred from chronic treatment with iodine and is associated with autoimmunity [59].…”

“…Hypothyroidism has also occurred from chronic treatment with iodine and is associated with autoimmunity [59]. Spallek et al reviewed the results of adverse effects from repeated doses with KI, iodide deficient population sensitivities to iodine, case studies of adverse effects, and the use of KI in Poland after the Chernobyl nuclear power plant accident [59]. They concluded that newborns and young children are most vulnerable to radioiodines and are also the group who experience a low frequency of adverse effects from KI.…”

Radiation Exposure and Thyroid Cancer Risk After the Fukushima Nuclear Power Plant Accident in Comparison with the Chernobyl Accident

“…This accident again highlighted issues regarding countermeasures, including iodine thyroid blocking, since suitable medication with stable iodine is effective for reduction and prevention of the internal exposure to radioactive iodine immediately before or after an accident (5) , and the safety control of food restricting consumption of contaminated milk and other products need to be put into practice after that. Although the side effects and effectiveness of iodine tablet dosage needs to be verified (6) , appropriateness of actual implementation of iodine thyroid blocking in Fukushima should be further evaluated. The outline on the nuclear accident in Fukushima and thyroid cancer risk will be summarized, assuming the possibility of the initial exposure to radioactive iodine, and drawing lessons from the Chernobyl nuclear power plant accident, referring our previous review article (7) .…”

Thyroid blockade in 123I-mIBG cardiac imaging: A common sense approach

“…While the large majority of patients who receive Lugol's or SSKI tolerate these agents, some patients find them unpleasant and a few could potentially become ill or manifest an allergy that was not previously known or suspected. 14,15 Particularly in older patients undergoing cardiac 123 I-mIBG imaging using radiopharmaceutical produced under Good Manufacturing Practice standards, both the risk from use of thyroid blockade and the benefit from limiting thyroid radiation dose are small. The clinician should consider individualizing use of thyroid blockade with 123 I-mIBG imaging to meet the needs of the patient, whether this involves use of such pretreatment or not.…”