W. H. ADAMS: LATE MEDICAL CONSEQUENCESOF EXPOSURE TO RADIOACTIVE
Hypothyroidism, Postsurgical
Despite efforts to mitigate loss of thyroid tissue, however, there continues to be evidence of
an inordinantly high frequency of postsurgical thyroid hypofunction among the exposed population.
Table 9 showsdata obtained through 1987 illustrating this point. An increase in frequency of
Table 9
Marshallese with previously normal TSH levels who have developed
elevated levels following thyroid surgery
Exposure
Adult
Number
Number
group
thyroid
with
with
Percent
dose (rad)*
surgery
hypothyroidism**
Rongelap***
1200
23
14
61
Utirik
160
25
7
28
Comparison
None
11
1
8
* Average estimated dose for an adult male
** Biochemical evidence of thyroid hypofunction as indicated by at least two determinations
of thyroid stimulating hormone > 7.0 uU/1. Normalvaluesare less than 6.0 uU/1.
*** Routine thyroxin suppression prescribed.
postsurgical thyroid hypofunction with increase in thyroid radiation dose is apparent, even though
all thyroid surgery patients were advised to take thyroxin. However, the data in Table 9 must
represent a minimum estimate of the prevalence of postsurgical thyroid hypofunction, for thyroxin
was not purposely discontinued before testing. Some persons may have maintained normal serum
levels of thyroid hormoneafter surgery only because they are adhering satisfactorily to the
prescribed thyroxin regimen. In conclusion, these data reveal an inordinantly high frequency of
postsurgical thyroid hypofunction in exposed persons whohad normalthyroid function prior to
surgery. Therefore, there appears to be significantly diminished thyroid reserve in many exposed
persons, and althoughthis diminution is not apparent from routine testing of hormone levels, it
frequently can be clinically unmasked by thyroid surgery.
M3
288