~i
on
50
¥G by RIA (ng/ml)
Thyroid iesions
(Rongelap + Uunk)
Nolesions (Rongelap)
\
A4 U\S. normal
Percent
30r
Basal
<5
10
1
2
ng, ml
2
30
3
0<
8 hr
24 hr basal
Post TSH
8hr
2+ hr
Figure 42. Effect of TSH administration on thyroglobulin
levels, 1973. =, Persons with thyroid lesions (Rong@lap
plus Uurik); @, without lesions (Rongelap).
Figure 41. Percentages of people in various groups having
given levels of thyroglobulin (by RIA), 1973.
and a high incidenceof parasitic infections. A pre-
liminary examination of North Americans with
abnormalleukocyte counts, however, did not show
a correlation between leukocytosis and iodoprotein level. Furtiter studies on this are indicated.
The chemical natureof this iodoproteinis also unknown. By analogy with findings in various thyroid diseases,9? the iodoproteinis likely to be comprised mainly of iodoalbumin arising from the
iodination of serum proteins.
It is now recognized, however, that thyroglobulin (TG) is a minor componentof normal plasma.
Ata reported concentration of 5.10.49 (S.E.M.)
ng/ml (range <1.6 to 20.7) in normal North
Americans,93 and assuming an iodine contentof
0.5%, this would be equivalent to an iodoprotein
iodine level of 2.60.25 ng/dl. Although it seems
unlikely, a preort, that circulating thyroglobulin in
the Marshallese could be elevated enoughto give
an iodoprotein level of 3 to 4 wg/dil(i.e., >500 ue
TG/d)), the possibility was investigated by radioim-
munoassay measurements (M. Izumi, J. Bautieu,
AND J. Rossins, unpublished observations, 1974;
see Figure 41). The assay could detect TG levels
>5 ng/ml; levels >40 ng/ml were not quantitated.
In the Rongelap and Utirik groups without thyroid lesions (47 and 25 subjects respectively), 2 80%
of the values were within the U.S. range, and no
correlation was seen between elevated serum iodoprotein and abnormal TGlevels. A few members
of each group, including the U.S. normal group,
had TG values >30 ng/ml, but the significance of °
this is uncertain. Of 24 subjects with elevated serum
iodoprotein, only | had serum TG >30 ng/dl.
A striking finding (Figure 41) was that in the
Rongelap plus Utirik group with thyroid lesions
(36 people) almost 50% of the levels were <5
ng/ml, a much higher percentage than in the other
groups. Most of these people had had prior thyroid surgery or were athyreotic, and it is presumed
that they hadinsufficient thyroid tissue for normal
TGproduction. Furthermore, T4 suppression therapy may haveionato the low TG levels in
the Rongelap peop
3 ES
TG was also measured beforeandafter TSH
injection in 10 Rongelapplus Utirik subjects with
thyroidlesions an@in 20Rongelapese with none
(Figure 42). In every case, TSH resulted in a mse
in TG level, and there was+NO,agpparent difference
between thetwo’
The unusualfy- nigh level ofiaidoprotein ii n the
Marshall
ies arein P
ypleis intriguing, and further studb, with 129] used asthe tracer, in
an attesnpe
tescetghty =
the protege
3="
ao
+ Be ~» =
—
G. CORSELATION ¢OF THYROID"ABNORMALITIES
<>WITHRADIATION EXPOSURE
Statisied on the incidence of thyroid abnormalities in people living on the Marshall Islands are
*Miss R.F. Straub, BNL, is doing’the chemicalanalvses.