Original Contributions




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.
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


children about ten years after expo-

‘ sure, and it was thoughtinitially that

JAMA, March 19, 1982—Vol 247, No. 11


these tests have been of a prospective
nature, and a limited number were retrospective.
Retrospective Analyses


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


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




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


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