28
devoid of physiological activity. Hence an iodoprotein containing only these iodoaminoacidsis
near the normally high Marshallese values (a) in
cases which had been on suppressive thyroxine
therapy, (b) in cases with atrophic glands due to
likely to bealso physiologically inactive. The
reason these individuals have such an iodoprotein
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 Marshalleseis of interest but may
be an unrelated phenomenon. It will be important
to see in future studies whether the iodoprotein
can be labeled with radioiodine.
The data on urine icdine 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 sourcesof
animal protein. Furthermore, these people are
in the bloodiis not clear. The data on normal controls from the Eastern United States, who showed
0.80 ug% iodoprotein iodine-in their serum,suggest thatit is a normal, albeit minor, constituent.
The method of chromatography employed is such
that well under 5% (or 0.2 ug%) of serum thyroxine iodine appears in the unretarded oriodo-
protein fraction. Therefore, the finding of iodo-
protem does not appear to be a methodologic
artifacts”..
More)recently, with the developmentof thyroid
abnormalities in the exposed Marshallese (to be
described), it was possible to examine serum iodo-
protein levels in cases with thyroid hypofunction.
These data are presented in Table 16. It seems
constantly exposed to sea spray, since the island
at its widest is about 4 mile across, and its highest
likely that the source of the iodoprotein was largely
cxtrathyroidal,since the levels of lodoprotein.were
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ao
*"1.TRyroxinte stoppedsever alsWORESefore sampling.
{Treated with v-thyroxine, 0.2 mg per day, for 6
months. Values in brackets are determination made prior
to starting thyroxine treatment (1965).
mee
:
andelevated thyroid10¢ ine secretion rate.
ever, as noted above,it seems somewhat morelikely that the serum iodoprotein is not of thyroidal
origin.