Radiation Linked to Thyroid Nodules in Atomic Bomb Survivors

NEW YORK MAR 01, 2006(Reuters Health) - In a study of Hiroshima and Nagasaki atomic bomb survivors, researchers have found a direct association between radiation dose and the occurrence of thyroid nodules, both benign and malignant.  By contrast, no clear association was seen between exposure and autoimmune thyroid diseases.

As reported in the Journal of the American Medical Association for March 1st, Dr. Misa Imaizumi, from the Radiation Effects Research Foundation in Nagasaki, Japan, and colleagues assessed the prevalence of thyroid disease in 4091 atomic bomb survivors whose radiation exposures occurred more than 50 years in the past. 

Nearly 45% of subjects had thyroid disease, including 32.2% of men and 51.0% of women, the report indicates. 

The estimated radiation dose received was directly linked to the prevalence of all solid nodules, malignant tumors, benign nodules, and cysts (p < 0.001).  The authors estimate that 28% of all solid nodules, 37% of malignant tumors, 31% of benign nodules, and 25% of cysts involved radiation exposures at mean and median doses of 0.449 and 0.087 Sv, respectively.

As noted, a direct dose-response relationship was not observed for autoimmune thyroid diseases, including Graves disease and antithyroid antibody-positive hypothyroidism.

"This is the first comprehensive thyroid disease screening study for both Hiroshima and Nagasaki atomic bomb survivors," the investigators point out. 

The results suggest that "careful examination of the thyroid is still important long after radiation exposure, especially for people exposed at younger ages."

In a related editorial, Dr. John D. Boice, Jr. of the International Epidemiology Institute in Rockville, Maryland, comments that "it is remarkable that a biological effect from a single brief environmental exposure nearly 60 years in the past is still present and can be detected."

He adds that "the absence of a dose-response relationship for any measure of autoimmune disease...is consistent with earlier studies."

SOURCE:

• JAMA 2006;295:1011-1022,1060-1061.