Table 15
NO. OF CASES
Kinetic Studies With **71
PROTEIN - BOUND
IODINE, #9 %
Figure 21.
creased the backgroundslightly. Mathematical
analysis* of these data was done on an IBM 7094
computerwith the program of Bermanetal.** No
Group
An*
Agi **
Marshallese
U.S. normals
0.72
1.0
0.97
2.0
Theoretical
No.
uptake
o,f
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.
tValue derived by the computer for the fraction of
extrathyroidal iodide ‘‘seen” by the counter.
somewhathigherthan similar ones calculated for
other groupsbut is not extraordinarily high.**-*’
Serum Cholesterol. Serum cholesterol determi-
the computer program adjusted the readings over
the neck for this factor. A least-squaresbestfit, as-
nations 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. Although the cholesterol levels in the
exposed group are about 17% belowthelevels in
cretion of iodide, produced a “best” value for this
significant at the 5% level. Individual values were
experimental correction was madefor extrathyroidal radioactivity ‘‘seen” by the counter, since
suming exponential thyroid uptake and renal exfactor, termed 63).
Theresults of the studies with '**] 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 thy-
roid uptake andtherate of urinary excretion are
both decreased. Since they are decreased more or
less proportionately, the calculated asymptotic up-
take is normalorslightly elevated. One may use
these data plus the urine iodide values to calculate
the averagedaily secretion of thyroid hormone,
assumingsteadystate conditions, using the formula
EU
S=Ty
where
S = amountofiodine secreted by the thyroid
(ug/day),
U = fractional thyroid uptakeofiodine, and
£ = urinary iodine (g/day).
With £=105 pg/day and U=0.42, the valuefor §
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.
the unexposed group, the difference is not quite
not indicative of thyroid disease.
Discussion of Previous Thyroid Studies.
Until
the recent developmentof hypothyroidism in two
boys, it had been the concensusofall physicians
who examined these people that they were euthy-
roid. A conceivable explanation for the high PBI
could be an elevation of thyroxine-binding pro-
teins in serum which, as in the congenitalelevation 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 mea-
sured by Robbins, however, were within normal
limits. The discrepancy between PBI and BEIsuggested the presence of an iodoprotein in serum.
The chromatography of serum iodine showing an
iodoprotein level in the Rongelap people of 2.2
pe% (and higherin the Utirik people) seemsto
implicate the iodoprotein as the cause for the elevated PBI.
No adequate dataare available on thecalorigenic potency of serum iodoproteins, but there are
some results which show that mostof the iodinated
amino acids in this protein are monoiodotyrosine
and duodotyrosine.**-*° These iodoamino acids are