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Original Contributions
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THE JOUANAL of the
American Medical Association
March 19, 1382
AQ 180.5
Vol 247, No. 11
Thyroid Hypofunction After Exposure to
Fallout From a Hydrogen Bomb Explosion
P. Reed Larsen, MD; Robert A. Conard, MD; Knud D. Knudsen, MD; Jacob Robbins, MD;
Jan Wolff, MD, PhD; J. Edward Rall, MD; John T. Nicoloff, MD; Brown M. Dobyns, MD
® Thyroid function was evajuated in the Marshaliese who were accidental
ly exposed to fallout-containing radiciodine isotapes in 1954. Measuraments
of thyrotrophin (TSH, thyroid-stimulating hormone) levels and free thyroxine
(T,) index (FT,!) have revealed that, among 86 persons exposed on Rongelap
and Ailingnae atolis, 14 have shown evidence of thyroid hypofunction. This
these were the only two persons so
of these showed clinical evidence of hypothyroidism. The most marked TSH
elevations were noted in nine persons exposed whan youngar than 6 years,
with estimated dosasto the thyroid fram 390 to 2,100 rad. Most of this group
subsequently had surgery for removal of thyroid nodules. The remaining five
cases hava been noted more recently among 36 surviving adults exposed at
an older age who showed no other detectable thyroid abnormalities. This
group had received estimated thyroid doses ranging from 135 to 335 rad and
showed modast elevation of serum TSH levels (6 to 9 pU/mL) and a slightly
subnormal FT,!. No abnormalities were found in persons on Utirik who
received substantially less radiation, and hypothyroidism was presant in less
than 1% of the control, unexposed Marshallese. The high prevalence of a
thyroid hypofunction in these persons indicates that this condition, as well as
thyroid nodularity, can be a delayed camplication of exposure to early fallout
from a nuclear explosion. The fact that a significant fraction of the radiation
report summarizes the results of
these studies, which indicate that, in
- was first noted in someindividuals about ten years after exposure. Only two
to the thyroid was from short-lived radioiodine tsotopes (Il,i, *"l), as
opposed to ""'l, may account for the severity of the thyroid damage.
affected." With current laboratory
techniques, it has been possible, both
retrospectively and prospectively, to
evaluate others of the exposed group
for thyroid dysfunction.” The present
addition to neoplasia, hypothyroidism
is a complication that has occurred in
a Significant fraction of this population.
METHODS
Several types of thyroid function testing
were performed during the annual or
’ semiannual
tienda Mt BD GL late
Bikini Atoll in 1954 have been summarized previously.” Because radioactive isotopes of iodine were present in
the fallout, a careful survey of ‘these
ing the accidental exposure of 250
Marshallese people to fallout after
the detonation of an approximately
15-megaton thermonuclear device at
persons for potential thyroid abnor-
malities has been performed on a
regular basis since that time. Thyroidal complications were first recog-
From the Howard Hughea Medica! Institute
Laboratory, Department of Madicine, Brigham and
Women's Hospital and Harvard Medical School,
Baston (Or Larsen); Brookhaven National Laboratory, Upton, NY (Drs Conard and Knudsen); the
nized about ten years after exposure,
when both primary hypothyroidism
and thyroid nodules were discovered.’ Benign and malignant thyroid
tumors are an expected complication
of thyroid radiation, particularly in
young people.“ Obvious clinical hypothyroidism was detected in two of the
National Institute of Arthritis, Metabolism, and
Digestive Diseases, Bethesda, Md (Ora Robbins,
Wolff, and Hall); the Division of Endocrinology,
Department of Medicina, University of Southam
California, Los Angeles {Or Nicolot{); and the
Ve ed gyie
Department of Surgery, Case-Western Reserve
JU eoGS
Hy
children about ten years after expo-
‘ sure, and it was thoughtinitially that
JAMA, March 19, 1982—Vol 247, No. 11
”
Brookhaven
these tests have been of a prospective
nature, and a limited number were retrospective.
Retrospective Analyses
THE CIRCUMSTANCES surround-
02115 (Or Larsen).
of the
team to the Marshall Islands. Most of
(JAMA 1982;247:157 1-1575)
University, Claveland (Or Dobyns).
Reprint requasts to the Thyroid Diagnostic
Center, Departmant of Madicins, Brigham and
Women’s Hospital, 75 Francis S!, Boston, MA
visits
National Laboratory (Upton, NY) medical
’ Fortunately, some unused samples of
plasma obtained for thyroxine (T.) measurements as long ago as 1963 had been
preserved in a frozen state at Brookhaven
National Laboratory. These samples were
analyzed using the following tests: plasma
T., thyroxine-binding globulin index.
(TBGI, a normalized triiodothyronine [T,]
charcoal uptake), and plasma thyrotrophin
(TSH,
thyroid-stimulating
hor-
mone).'""" While the stability of TSH under
these circumstances is not known, one
sample from 1963 had a TSH concentration of 500 .U/mL, suggesting that such
Measurements are reasonable. The free
thyroxine index (FTI) was the product of
the T, and TBGI. The normal ranges for
these determinations in the US population
are as follows: plasma T., 5 to 10.2 yg of T,
per deciliter, TBGI, 0.85 to 1.10 units; PT.L
4.7 to 9.7 units; and plasma TSH,less than
Hypothyroidism and Fallout Exposure—Larsen et al
1571