NATIONAL INSTITUTES OF HEALTH CLINICAL STAFF
TABLE 5.
Date
Serum Iodide Measurements in the Marshall Islands
Group
No.
Samples
Protein-boundiodine, ug/100 ml
1959
Marshallese
1962
Marshallese
1964
1965
12
14
Medical team
Marshallese-—exposed
1965
Marshallese—unexposed
level and individual values going up well
into the hyperthyroid range.
In 1965 a comparison was carried out between exposed and nonexposed individuals; there was no difference between them.
One evaluation of the butanol extractable
serum iodine (BEI) done as far back as
1959 indicated that the BEI—which would
be the hormonal. iodine—was.in the nor-
mal range for North America, suggesting
that the elevated PBI was not thyroxinelike. Figure 14 shows the distribution of the
PBI in the population. The valley at one
point was thought to be an artifact due to
the small number of individuals sampled,
and it was concluded that the PBI levels
formed a normal distribution. There was
no bimodal distribution or any familial
# 8
CASES
6
8
10
PBI 9/00 m
l2
Ficure 14. Distribution of serum protein-bound
iodine in Marshallese individuals. Reproduced with
permission from Rall and Conard: Amer. J. Med.
40: 882, 1966 (12).
Average
Range
Percent
Over 8 ug/
100 ml
6.2
8.6
4.1-9.2
4.6-12.0
16
64
3.9-10.7
28
10
31
4.9
7.6
2.5-6.9
4.1-11.9
12
49
2.7~-8.7
19
Butanol extractable iodine, ug/ 100 ml
1959
Marshallese
4
Internal Apzals,of
7.0
0
42
prevalence that would indicate a genetic
abnormality or any evidence of two genetic
populations in the Islands with respect to
PBIlevels in blood.
Table 6 shows somelater studies in which
chromatography on Dowex-] columns was
performed in order to identify the nonhormonal iodine in serum. This procedure
(15) separates iodoprotein from iodoamino
acids not in peptide linkage. In North
Americans (these were normal controls
drawn at the NIH) the iodoprotein averaged 0.8 »g/100 ml, whereas in the Marshallese the value was considerably higher
with a mean of 2.2 yg/100 ml. The thyroxine iodine average was slightly higher
in the Marshallese but probably not significantly.
Recently, with the development of thyroid abnormalities in the exposed Marshallese, it was possible to examine serum iodoprotein levels in patients with thyroid
hypofunction. The results, presented in
Table 7, suggest that the iodoprotein was
largely from an extrathyroidal source since
the level wasstill elevated in patients with
atrophic thyroid glands due to radiation
(Cases 3 and 5); in thyroidectomized patients, one of whom (Case 69) had little, if
any, uptake of 487] into the thyroid (as we
will discuss later); and in subjects who had
been on suppressive therapy with levothyroxine.
Dr. Conard mentioned that the iodine
analyses of urine, which were carried out
anasiadioadicdilial
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