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LARSEN etal.
The present studies suggest that there is a significant risk of development
of impaired thyroid function many years following estimated thyroid doses of
less than 500 rads from the mixture of radioiodines present in fall-out from
nuclear detonations. In the Rongelap and Ailingnae groups, the effect has
apparently not been significantly severe as to result in clinically evident hypothyroidism, but by currently accepted criteria there is evidence of impaired
thyroid reserve in these subjects. If left untreated, it would be expected that
thyroid function would continue to decrease in such subjects to the point of
clinical hypothyroidism. The data in Table VI also indicate that the frequency
of an elevated serum TSH, the earliest biochemical evidence of impaired thyroid
function,is also significantly more commonin the exposed Rongelap population
than in the control-unexposed group. There are several other exposed Rongelap
individuals in whom results of basal TSH and at least one TRH test have suggested
the possibility that they may also have evidence of impaired thyroid function.
These individuals are currently undergoing repeated testing to determine whether
or not this preliminary evidence of thyroid dysfunction can be confirmed.
In summary, these data indicate that in addition to thyroid nodularity, a
well-recognized manifestation of exposure of the thyroid to radioactive iodine
or external radiation, biochemical evidence of thyroid dysfunction can appear
as long as 25 years after thyroid doses as low as 350 rads.
ACKNOWLEDGEMENTS
This work was supported in part by the: Department of Energy.
P.R. Larsen is an investigator, Howard Hughes Medical Institute.
Weare grateful to S.T. Bigos for allowing us to review Ref. [11] before its
publication.
REFERENCES
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exposure to radioactive fallout”, Radiation-Associated Thyroid Carcinoma (DE GROOT,
J., Ed.), Grune & Stratton, New York (1977) 241.
[2] CONARD,R.A., et al., A Twenty Year Review of Medical Findings in a Marshallese
Population accidentally exposed to Radioactive Fallout, Rep. BNL 50424, Brookhaven
National Laboratory, Upton, New York (Sep. 1975).
[3] CONARD,R.A., Acute myelogenous leukemia following fallout radiation exposure,
J.Am. Med. Assoc. 232 (1975) 1356.
{4] SUTOW, W.W., CONARD, R.A., “The effects of fallout radiation on Marshallese
children”, Radiation Biology of the Fetal and Juvenile Mammal(Proc. 9th Ann.
Hanford Biology Symp.Richland, 1969) (1969) 661.
{5}
RALL, J.E., CONARD,R.A., Elevation of the serum protein-bound iodine level in
inhabitants of the Marshall Islands, Am. J. Med. 40 (1966) 883.
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