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NATIONAL INSTITUTES OF HEALTH™GLINICAL. ‘STAFF
could not test for an organification defect.
It is probably a dose effect.
Dr. WELLINGTON Moore: We investigated chromosomechanges in Chinese ham-
ster thyroid cells after the administration
of different doses of '1I to animals 7 to 10
days of age. Thirty days and a year after
injection the thyroids were removed, trypsinized, and cells grown in tissue culture
for 3 days. The cells were arrested in metaphase, fixed, and stained for chomosomal
analysis. It was found that thyroid cells
were quite sensitive to irradiation. Doses
as low as 6 rads produced a tenfold in-
crease in the number of cells containing
aberrations at 30 days (3.3% versus 0.31%
in the control cells). Twenty-five percent of
the thyroid cells contained aberrations at
a dose of approximately 1,000 rads at 30
days. After 1 year the aberration rate had
decreased by three- to fourfold. This was
due in part to the increase in gland size
associated with the normal growth of the
animals. The persistence of the aberrant
thyroid cells (approximately one third of
the life span) suggests that some of these
damaged cells may persist for the remainder of the animal's life.
Dr. Rospsins: Thank you for the comment. That is another area I did not get
into because of time. It is of tnterest that
Drs. A. A. Al-Saadi and W. H. Bierwaltes
at the University of Michigan School of
Medicine have been studying chromosomal
aberrations in animals and find aberrations
resulting from iodine deficiency and other
forms of thyroid stimulation, so they may
not be limited to radiation effects, although
certainly that could be a contributing
cause.
Dr. Conarp: Attempts were made to do
chromosome studies on cultured thyroid
tissue from the operative specimens on the
Marshailese. Unfortunately, they were not
:
a
.
Annals of
Internal Medicine
a
ne Vago. SUMMARY
aged further, but the Marshallese who had
greater damage had no uptake, and so we
The presence of radioactive isotopes of
iodine in fallout from atomic explosionsis
well known. Inthe accidental exposure of
the inhabitants of one of the Marshall
Island after a fusion-type explosion in
1954, thyroid radiation from radioiodine,
particularly in the children, was sizable.
This resulted in the late development of
thyroid insufficiency or thyroid nodules or
both in 80% of those children exposed at
less than 10 years of age. At the present
time,
the
thyroid
effects
constitute
the
only important overt medical problem in
the exposed population. Detection of thyroid damage was hindered by its tnsidious
onset and by the unexpected occurrence of
elevated blood levels of iodoprotein in the
Marshallese population. The greater prevalence of thyroid abnormality in the children is probably due to two factors: a
larger radiation dose due to small thyroid
size and a greater likelihood of the growing organ to manifest changes resulting
from chromosomal alterations. The spectrum of radiation exposure of the thyroid
glands in any population is very wide,
ranging from stratospheric fallout from
atomic explosions and clinical testing with
radioiodine isotopes to high radiation rates
intentionally produced in therapy of thy-
roid diseases. The Marshal] Istand expert-
ence will help to define the range in which
significant thyroid damage mayoccur.
ACKNOWLEDGMENTS
Weare deeply indebted to the many members of the medical survey teams over the past
12 years for their participation and for the material presented here. We are also grateful to
many other people for invaluable advice and
assistance, including Drs. C. L. Dunham and
H. D. Bruner of the Atomic Energy Commission; Drs, V. P. Bond, E. P. Cronkite, H. A.
Johnson, L. K. Dahl, J. E. Jesseph, and H. L.
Atkins of Brookhaven National Laboratory;
Drs. S. Warren, B. P. Colcock, and W. A.
Meisnner of Boston; Drs. G. H. Klinck, E. D.
Henley, C. J. Stah!, C. A. Broaddus, S. Lindsay,
and A. Hicking; and to other members of the
ae ne yea ore
successful.
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