27
we
Table 15
NO. OF CASES
ee cae
em ae,
- Kinetic Studies With '"I
Le nen
s
+
4
k.
aimaifnter
an
6
8
i)
PROTEIN-BOUND IODINE, nq %
12
Figure 21.
creased the backgroundslightly. Mathematical
analysis* of these data was done on an IBM 7094
computer with the program of Bermanet al.** No
experimental correction was madefor extrathyroidal radioactivity “‘seen”’ by the counter, since
the computer program adjusted the readings over
the neck for this factor. A least-squares bestfit, assuming exponential thyroid uptake and renal excretion of iodide, produced a “best” valuefor this
Theresults of the studies with ‘**I are shown in
Table 15, where they are compared with values
obtained from normalindividuals residing in the
United States. It can be seen that the rate of thyroid uptake and the rate of urinary excretion are
both decreased. Since they are decreasedsmore or
le
ha*
Ag **
Marshallese
0.72
0.97
U.S. normals
1.0
2.0
Theoretical
No.
uptake
a,,{
cases
42%
33%
0.08
-
21
-
“Fraction of extrathyroidal iodide transferred to the
thyroid per day.
**Fraction of extrathyroidal iodide excreted in the urine
per day.
{Value derived by the computer for the fraction of
extrathyroidal iodide “seen” by the counter.
=
factor, termed o;,.
+ mene te
Group
less proportionately, the calculated asympfotic uptake is normal or slightly elevated. One may use
these data plus the urine iodide valuesto calculate
the averagedaily secretion of thyroid hormone,
assuming steady state conditions, using the formula
EU
S=T=o
where
S = amount of iodine secreted by the thyroid
(ug/day),
U = fractional thyroid uptake of iodine, and
E = urinary iodine (ug/day).
With £=105 pe/day and U=0.42, the value for S
is calculated to be 76 wg iodine/day. This valueis
*We are indebted to Dr. Mones Berman, National Institutes
of Health, Bethesda. for this analvsis.
I008311
somewhat higher than similar ones calculated for
other groups but is not extraordinarily high.*>*"
Serum Cholesterol. Serum cholesterol determinations on most of the exposed and an equal number of the unexposed population were carried out
in 1957 and 1959. The results are tabulated in Appendix 5. Althoughthe cholesterol levels in the
exposed group are about 17% belowthe levels in
the unexposed group,the difference is not quite
significant at the 5% level. Individual values weve
not indicative of thyroid disease.
Discussion of Previous Thyroid Studies. Until
the recent development of hypothyroidism in two
boys, it had been the concensusofall physicians
who examinedthese people that they were euthy-
roid. A conceivable explanation for the high PBI
could be an elevation of thyroxine-binding proteins in serum which,as in the congenital elevation of thyroxine-binding globulin described by
Beierwaltes and Robbins,** causes an increase in
the serum PBI without hyperthyroidism. The
levels of the TBG in the Marshallese serum measured by Robbins, however, were within normal
limits. The discrepancy between PBI and BEI suggested the presenceof an iodoprotein in serum.
The chromatography of serum iodine showing an
iodoprotein tevel in the Rongelap people of 2.2
ug % (and higherin the Utirik people) seemsto
implicate the iodoprotein as the cause for the elevated PBI.
No adequate data are available on the calorigenic potencyof serum iodoproteins, but there are
some results which show that most of the iodinated
aminoacidsin this protein are monoiodotyrosine
and diiodotyrosine.??*° These iodoamino acids are