associated with thyroid injury in some of the children, have been discussed in
detail in this report.
The greatest incidence of these abnormal_ties has been
in the higher-dose Rongelap group, particularly ia children exposed at <10
years of age, with less incidence in the Ailingnae group and least incidence
in the lower~-dose Utirik group. The recent development of thyroid nodules in
two Rongelap males exposed in utero indicates that radioiodines may be passed
from mother to fetus.
Almost all patients, including those in the unexposed group with thyroid
nodules, have had thyroid surgery in U.S. hospitals. A wide spectrum of lesions has been found.
Thyroid hypofunction, not related to thyroidectomy, was first noted in
two Rongelap boys who developed frank hypothyroidism with growth retardation.
Biochemical (subclinical) hypothyroidism has been roted in some prior to thy—
roid surgery for nodule removal. More recently, about 6 adults (5 Rorgelap,
1 Ailingnae), who received lower doses than the children and showed no detect-—
able thyroid nodularity, have developed biochemical hypothyroidism. No hypofunction of the thyroid has been detected in the exposed Utirik population.
C.
Comments
From the Marshallese experience it is clear that in any future accident
involving radioiodines the use of oral stable iodine to suppress radioiodine
uptake by the thyroid, particularly in children and pregnant women, should be
considered (249). To ascertain the degree of radioiodine absorption, it would
be helpful to have direct instrument readings over the thyroid, with leg or
arm readings as a control; also, urine levels of radioiodine would be helpful.
With regard to late effects in persons receiving significant radiation
doses to the whole body or thyroid, regular follow-up examinations should be
done over the ensuing years with particular attention to hematological status,
development of cancer, and thyroid abnormalities. Even though the prophylactic value of thyroid hormone treatment in preventing development of thyroid
abnormalities has not been proved in the Marshallese or other humans, such
treatment is sound and should be considered. During follow-up thyroid exam
inations, determination of serum TSH levels would be desirable, since the
Marshallese experience has shown this test to be a most sensitive indication
of reduced thyroid function. In addition, thyroid uptake studies of radioiodine and scans of the gland should be considered. Any distinct thyroid
nodules should be surgically removed. If thyroxin treatment is not already a
part of the treatment regimen, it should be instituted in surgical cases as
well as any cases showing deficiency of thyroid function. Patients who have
had malignant lesions removed should of course have regular follow-up
examinations.
Although the later development of thyroid malignancy is a serious problem, the consequences are not as likely to be fatal as those of other types of
malignancies. With the medical and surgical treatment of thyroid disease now
available, death associated with malignant tumors of the thyroid is unlikely
except in the case of the most malignant types, which appear to be rare in
irradiated groups.
As has been pointed out, the uncertainty of dose estimates in the
Marshallese hzs hampered evaluation of dose-response relationships,
~ 87 -