334
CONARD er al,
DISCUSSION
;
-
As a result of the exoosure of the Marshallese people to radioactive
Saiiout 15 years age the only late findings of significance have been
the development of thyroid abnormalities with resulting retardation of
growth and development in the more heavily exposed children.
The lack
of development of nodules in the unexposed and lesser exposed populations
in the same age range clearly indicates the etiological relationship of
the lesions to radiation.
‘The higher incidence of nodules in the children
than in adults is probably related to the larger dose of radiation re-
ceived by their smaller glands.
-
The high incidence of these lesions in
nee eee enti
5,6)
a
this population is perhans a little surprising in view of the consideration
of the dose and dose rate from radiofodine exposure in a fallout situation.
The fact that a large part of the dose was from short-lived radio-
iodines with fast dose rate may have been important.
The development of
these thyroid abnormalities is consistent with reports in the literature
on many animai studies and some human studies.77,8]
Sheline et al. [9'
Z
have reported the development of nodules in follow-up studies of children
for hyperthyroidism with radioiodine and more recently Pincus et al. 510?
have reported a high incidence of nodules in children who had been treated
with x-radiacion of the neck in infancy.
rr
The insidious onset ot thyrvid hypofunction and retardation of
grewt
in the Marshallese children was probably associated with the slow
loss of functioning thyroid cells through lack of replacement due fo
radiation impairment of cellular replication.
One can speculate that
less injured cells in the thyroid probably responded co the increased
TSH simulation and che picture of concomitant atrophy and hyperplasia
"9
+ tome
se
resulted in gross nodule formation,
In the 2 cases with complece
thyroid atrophy, however, there must have been sufficient radiation
damage to prevent appreciable responses to TSH stimulation,
No dvoube there is increased risk of cancer of the thyroid
in the
Marshallese children and it is perhaps chance that no such malignancies
have vet heen discovered.
The Literature is replete with many retrospective
as well ac prosnective studies which show the late development of cancer
of the thyroid ic children that had been treated with cervical irradiatien
during infaney and varly childhood.[ 11-13} Mowevur, there is scant evidence
as yet for the development of cancer of the thyroid following radioiodine
treatment.
Increased prevalence of cancer of the thyroid has been reported
{n adults exposed to the atomic bomb in Hiroshima !14] and other cypes of
radiation.{/15:
Ic is of course not possible to prove the causal relation-
ship of irradiation in the case of cancer of che thyroid in the exposed
women reported here, but in view of low incidence of such lesions in the
Marshallese, this possibility must be seriousiv considered.
"le
743
”
PLS
It is not «known whether treatment with thyroid hormone will reduce
the risk of cancer of the thyroid in the human being.
However, such
suppression has been teported to prevent the ceveicpment ef thyroid
nodules in rats.£16;
It is hoped that the hormone treatment being
given the Marshallese miy suppress such neoplasia from radiation.
REFERENCES
os
pee
aod
Load
Pie at
ee
[1]
‘CONARD, R.A., HICKING, A., Medical Findings in Marshallese people
exposed to fallout radiation:
(1965) 457.
results from ten-year study, JAMA 192
“45
.
[16