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rationing in order to provide the least-contaminated food to the young.
If only a highly-contaminated supply were available, the uptake by the
thyroid of 1131 could be blocked through administration of stable iodine.
In a study sponsored by the U.S. Public Health Service, 21 sodium
iodide was given in increasing doses to groups of children having normal thyroid function.
The size of the sodium-iodide dose was varied
in proportion to the skin area of the children.
Maximum suppression
of iodine-131 uptake was achieved with 1.5 to 2.0 milligrams of iodide
per square meter of body surface per day.
It quickly rebounded when
the iodide was discontinued.
Based upon this experience, the research team calculated that the
minimum dose of iodide required for almost complete suppression of
the uptake of radioactive iodine by the normal human thyroid was 1.5
to 2.0 milligrams per day per square meter of body surface.
Foran
adult, this dose of iodide would be 3 - 4 mg per day; and for children,
about 1 mg per day.
At these iodide doses, suppression of uptake of radioiodine would
begin almost immediately, and by 24 hours a 50% reduction would be
expected.
Subsequently, a gradual decrease in uptake to a minimum
of about 5% would occur in 4 - 6 weeks.
Toxic effects of iodide from
daily doses of this order of magnitude given over relatively short
periods of time would not be expected.