antimicrosomal antibodies.
While the role of
radiation exposure in producing this patient’s
illness is not certain, an argument can be made
for relating the two. Further observation may
documentthe true nature of the thyroid hormone
fluctuations in this patient. Since an increase in
risk of hypothyroidism might be attributed to
radiation exposures as low as 20 cGy (Maxonet
al., 1977), the patient clearly was at risk for
developing the disorder.
Other laboratory results:
Appendix B also includes results of other tests
that are performed on manyorall of the exposed
persons. Several of these tests have been used to
screen for occult malignant disease. Although
there is no general marker for malignancy, the
clinical justification for, and the results of, those
tests are described here.
Serum protein electrophoresis
Multiple myelomais one of the hematological
malignancies that has been determined to be
inducible by radiation (Cuzick, 1981).
This
interpretation is strengthened by findings in
Japanese atomic bomb survivors, although the
effect of radiation was not detectable until about
20 years after exposure (Ichimaru et al., 1982).
The production of a monoclonal protein
detectable by serum electrophoresis often
precedes by years the other clinical manifestations
of multiple myeloma. Although the risk of
myelomais small, serum protein electrophoresis
is performed on the exposed Marshallese about
every three years in order to detect the early
appearance of a monoclonal protein.
If a
monoclonal spike were to be found in a patient’s
serum, it would not necessarily indicate the
presence of myeloma. Conversely, the absence of
such a spike does not rule out myeloma.
Nevertheless,it is used as a screening test, and no
monoclonal proteins were detected during the
1989 serum testing of the Marshallese sera.
In common with many populations in tfopical
regions, the Marshallese have relativel
globulin levels. This increase is polyclonal,
cause is unknown.
Serum calcium
An endocrinological disorder that ha
thought to be associated with both exter
internal }'{ radiation is hyperparath
(Cohen,et al., 1990; Rosen et al., 1984).
dependent increase in the
inciden
hyperparathyroidism has also been reporged in
Japanese atomic bomb survivors (Fujiwarafetal.,
1990). In all three cited studies, paratfyroid
adenomas were present in most patients. Sqme of
the exposed Marshallese received large radiation
doses to the parathyroid gland, as well af) high
external doses. Furthermore, the susceptibflity of
Marshallese to this effect of radiation is unKinown.
Therefore, serum calcium levels are checked every
three years. No elevated levels were ddfected
during the 1989 survey.
Serum aipha-fetoprotein
Thereis a high risk of hepatocellular car
in persons who remain persistently positife for
hepatitis B surface antigen. The last Brookhaven
medical program report discussed this dise[se in
relation to the exposed Marshallese,
the
prevalence of serologic evidence of hepatjtis B
infection in the Marshall Islands is veryg high
(Adams et al., 1986). In some instanceg it is
possible to identify hepatocellular carcinomajat an
early stage by testing serum for alpha-fetopsotein.
This might permit identification of the tumop at a
stage when it is still resectable. Therefoge, all
exposed and unexposed persons who are kn
to
the medical program to be seropositive for hepatitis
B surface antigen have alpha-fetoprotein flevels
performed annually.
=
Thus, this patient’s thyroid function tests have
been on the low side of normal and occasionally
overtly low for many years.
Transient
hypothyroidism persisting for many years has been
reported with chronic autoimmune thyroiditis
(Takasu et al., 1992). However, the Utirik patient
had no. detectable antithyroglobulin or
Erythrocyte macrocytosis
The many causes of macrocytosis include s#veral
premalignant and malignant hematologic disases.
Therefore, erythrocyte size is, checked anrpally.
unexplained or irreversible macrocytosis]
detected in the exposed population. Those el
levels that were found appear to have been
was
B12) or chronically excessive ingestion ofalc
12
Fan