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Table 1.—Thyroidal Radiation Dose Estimates and Thyroid Nocularity,
Exposed and Control Marshallese Population, 1978
sured using commercial kits.
Prospective Studies
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1 to 6 pU/mL. Antithyroid microsome and
antithyroglobulin antibodies were mea-
Plasma T., TBGI, and TSH levels were
evaluated regularly in persons who had
had thyroid surgery and who werereceiv-
ing levothyroxine sodium replacement
therapy. In persons ‘not operated on, pro-
phylactic levothyroxine sodium replacement was discontioued for a period of two
to four months, and baseline thyroid function studies, a thyrotrophin-releasing hormone (TRH, protirelin) stimulation test
(500 yg of protirelin intravenously {TV}
followed by a plasma TSH measurement
20 minutes later), and, in some persons, a
TSH stimulation test (10 units of bovine
thyrotrophin given intramuscularly [131]
followed by a plasma T, measurement 24
hours fater) were performed.
Thyroid Dasimetry
Rongelap and Ailingnae are about 100
nautical miles east of the detonation site
on Bikini, and fallout began on these two’
islands four to six hours after the explosion. Utirik is 175 miles further east, and
the fallout appeared there 22 hours after
the detonation. The Marshallese were evacuated from these three islands about 48
hours after the fallout first appeared. The
_ dose to the thyroid of the Rongelap people
was estimated from the I in a pooled
“nrine sample collected 15 days after the
exposure.” The amount of "I in the thy-
roid of these subjects on the first day of
"fallout was estimated to be 11.2 wCi (5.6 to
22.4 pCi), assuming that 0.1% (range,
0.05% to 0.2%) of the maximum thyrcidal
Iwas excreted in the-urine on the 15th
day.” The quantities of shorter-lived
iodine isotopes ("I half-life [t], 25
hours; '"I t#, 21 hours; and '"I th, 6.7
hours), which are produced in the initial
fission process, could not be measured. The
dose to the thyroid from these isotopes
was calculated to be as much as three
times that received from '"I.”
The thyroid dose to the Rongelap adult
{including external + radiation) was esti-
mated to be 335 rad (220 to 450 rad) (Table
1). Because of the smaller size of the
_ thyroid gland in children, the dose due to a
given quantity of thyroid radioiodine was
larger than in adults.” A 3-year-old child
was thought to have received a thyroid
dose of 700 to 1,400 rad, and a l-year-old,
2,000 or more rad. In addition to the
variables of gland size, and the prevalence
of short-lived isotopes of iodine, a major
uncertainty is in the quantity of radicac-
tive jodine ingested by different individu-
als from contaminated food and water
during the two days before their evacuation. All subjects received total-body irra-
1572
Age at
Exposure,
ye (7954)
n
<10
" 10-13
>18
.
;
7
. 22(3)"
12
33
_ 390-2, 100
" 935-810
353
Ailingnae (whole-body + dase, 69 rad)
<10
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'>18
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Unexposed
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10-138
>18
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Malignant Thyroid Nodules
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237
190
135 |
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.
275-450
.. tf
Uticik (whole-body + dose, 14 rad)
“10
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Surgery for Benign or
Dose, Rad
Rongelap (whole-body + dose, 175 rad}
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“Numbers in parentheses indicate persons exposed in utero.
diation from external sources that ranged
from 14 rad on Utirik to 175 rad on
Rongelap (Table 1). These estimates of +
Table 2.—Ptasma TSH Concantratians
in the Marshallese Population*
exposure have been thought to be reasonably accurate, since the observed hemato-
TSH.
RESULTS
Normal Values for Thyroid Function
Tests in the Marshallese Population
The plasma TSH concentration in
the control Marshallese population is
presented in Table 2. In 115 unex-
posed persons who were clinically
euthyroid, 11 subjects had a plasma
TSH concentration greater than 3
pU/mL. Only one of these was greater
than 6 pU/mL. This person was a
59-year-old woman (subject No. 982)
whose plasma TSH concentrations
over the past five years have ranged
between 6 and 7 «U/mL, and whose
most recent plasma 7, level was 6.4
ppe/aL; TBGI, 0.76 units; and FTI 4.9
units. Antimicrosomal and antithyroglobulin antibodies were not detected.
Evaluation of samples obtained from
99 Utirik subjects exposed to low
levels of radiation showed that a
similar fraction (12%) had plasma
TSH concentrations in excess of 3
pU/mL, but none was greater than 6
nU/mL. On the basis of these data, a
value of 6 nhU/mL or greater was
considered abnormal in the Marshallese population. In 12 unexposed,
euthyroid Marshallese, protirelin infusion studies were performed. The
plasma TSH 20 minutes after IV
TSH
Level
logic depression in the Rongelap people
was in general agreement with what
would have been predicted.”
JAMA, March 19, 1982—Vol 247, No. 11
SO; fabs
.
No, of Subjects Having
Estimated Thyraid
Level
fm >SpU/smb Ss all/mt
Contro!
unexposed 115
Utirik
exposed
99
ti
*
12
.
1
‘
o
"Samples obtained between 1975 and 1979.
' TSH indicates thyrotrophin (thyroid-stimulating
hormone).
infusion of 500 yg of protirelin was
10.824.7 pU/mL (SD) higher than
the basal level. Ten euthyroid unexposed Marshallese were given 10 units
of thyrotrophin IM and their plasma
T. levels were measured 24 hours
later. The mean initial plasma T,
concentration in this group of ten
subjects was 6.0+1.7 pe/dL, and the
mean T, increment after introduction
of thyrotrophin was 4.2+£13 pg/dL.
Thyroid Function After
Thyroid Surgery
In the last column of Table 1 are
shown the numbers of subjects who
have had thyroid surgery (usually
subtotal thyroidectomy) for benign or
malignant thyroid nodules. During
the period 1972 to 1974, plasma TSH
concentration was greater than 6 »U/
mL (range, 6.2 to 460 w«U/mL)in 11 of
20 Rongelap persons who had surgery
despite the prescribed levothyroxine
sodium replacement. The number of
subjects in whom the residual thyroid '
function was inadequate was higher
than expected. This suggested that
Hypothyroidism and Fallout Exposure—-Larsen et al