28
devoid of physiological activity. Hence an iodo-
protein containing onlythese iodoamino acidsis
likely to be-also physiglogically inactive. The
reason theseindividuals have such an iodoprotein
in the blood is not clear. The data on normal controls from the Eastern United States, who showed
0.80 ug% iodoproteiniodine in their séfum,sug-
gest thatit is a normal, albeit minor, constituent.
The method.of chromatography employed is such
that well under 5% (or 0.2 pge%) of serum thy-
roxine iodine appears in the unretardedor iodoprotein fraction. Therefore, the finding of iodoprotein does not appear to be a methodologic
artifi
More‘recently, with the developmentof thyroid
abnormalities in the exposed Marshallese (to be
described), it was possible to examine serum iodoprotein levels in cases with thyroid hypofunction.
These data are presented in Table 16. It seems
likely that the source of the iodoprotein waslargely
extrathyroidal, since the levels of iodoprotein were
near the normally high Marshallese values (a) in
cases which had been on suppressive thyroxine
therapy, (b) in cases with atrophic glands due to
radiation (subjects No. 3 and No. 5), and (c) in
thyroidectomized cases. The source of the iodoprotein is not known. The previously reported finding
of high plasma proteins,’ particularly gamma
globulins, in the Marshallese is of interest but may
be an unrelated phenomenon. It will be important
to see in future studies whetherthe iodoprotein
can be labeled with radioiodine.
The data on urine iodine show values in the
normal range. In general, it had been expected
that individuals living close to the sea and eating
seafood and fish would show relatively higher
iodine intake. The inhabitants of the Marshall
Islands have fish as one of their main sources of
animal protein. Furthermore, these people are
constantly exposed to sea spray, since the island
at its widest is about '4 mile across, andits highest
point is 20 ft above hightide.
The data:onprimary iadine were used with the
results
amount
to Thyront. Function
J Total
No.
iodine, -PRI,
ug
cee es
3°
5S
65
i7a.
7
a:
« »
age
<i
De
s
:
t
“32
gee B31
L Gi
2
10
aetLB
Fis
*Phyroidectomized**
te ALB <05
2°
Iodoprotein
T, adine, . ioding,*
Hypath¥toid
1,
6 Os
=6«<05
2.0
a SRD
>
(2.2)
(1.3)
| (1)
“
>1.3)
(>0.8}
ibe:
(By
3.2 [4.5]
3.8 [2.9]
ence between#
suredidirectly by
+41Thyroxifft
dine secreted daily by the
thyroid.
Thevalue 76"pg/day is.somewhat hehe the
Serum lodopiBtein Lévels in Relation
Subject”
ed with aEseudiestto calgulate the
3% fag/dayfound
Stanbury et'al.** ar
g/day
ie ‘by Fr
Ingbar** butloserto the
we 7
dayproposed by Riggs.*’ Unfortuae :
Bug is known aboutthe rate of turn-
sever ofthe serum iodoprotein.If it hasqnughly the
semgrate ofdegradation and the same volumeof
ition as thyroxine and it is asaymedgta have
in the thyxeid gland, then,
Marshallese thymids te
ould ex-
ANIC
portional to the level.eforganic iodine
/dditiongf odalippporine vatues
ave e levglsfor
Marshallese
multiplicationof the ratio by
‘Use. best.value. for iodine seca normal
ee 2.22+4.53
vac. 0.8043.Tex OSSva/ay.
This
ns Hhicy welliienthe76-yp/dy
lated independently frog rine;
studies and is compati with Flinical picture
eink
+Treated with t-thyroxine, 0.2 mg per day, for 6
months. Values in brackets are determination made prior
to starting thyroxine treatment (1965).
epasruthypid status
of amclevated PBI
elevatéd thyroid iodiffésecretion rate. However, as noted above, it seems somewhat morelike-
ly that the serum iodoprotein is not of thyroidal
origin.