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Re: KI

KI protects the thyroid gland only from the effects of radioactive 

iodine.  The thyroid gland concentrates iodide to use in the 

synthesis of the thyroid hormone thyroxine.  The gland thus needs 

iodine, and has a great affinity for it, concentrating it from the 

bloodstream.  If, however, a large dose of cold KI is given prior 

to exposure to radioiodine, the gland is swamped and can no longer 

accumulate iodide.

KI thus has no effect on other tissues of the body, or other 

radioisotopes.  Its use may therefore convey a false sense of 

security.  Radioiodine is known to induce thyroid tumors, both 

benign and malignant, especially in children.  There remains some 

question as to the sensitivity of the adult thyroid; it is 

certainly much less sensitive than the juvenile gland.  Prevention 

of this effect from KI loading is thus a benefit.  However, 

virtually all radiation-induced thyroid cancers are low grade, and 

are rarely fatal.  (There is some evidence from Chernobyl that 

disputes this last statement.)  Unfortunately other radioisotopes 

may induce cancers in other tissues that are much more virulent and 

much more frequently fatal.

Julian Gibbs



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S. Julian Gibbs, DDS, PhD               Voice: 615-322-1477

Professor, Emeritus

Dept. of Radiology & Radiological Sciences

Vanderbilt University Medical Center     Home: 615-356-3615

209 Oxford House        Email:s.julian.gibbs@vanderbilt.edu

Nashville TN 37232-4245     or alias:j.gibbs@vanderbilt.edu

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