CAMA
19 “84
IX.
It has been clearly
THYROID ABNURMALITIES*
demonstrated that the most serious late effects of
accidental exposure to fallout in the Marshallese residing on Rongelap and
Utirik Atolls on March 1,
1954, has been related to radiation injury to the
thyroid, as evidenced by development of nodularities and ypofunction of the
gland. Such injury was due to exposure to penetrating gemma radiation and internal absorption of radionuclides during the two-day period pricr to their
evacuation. In this section, thyroid effects are summarized. Fmphasis is on
the findings during the past seven years.
In Appendix II, the estinated thyroid doses are discussed. Since the principal effects of thyroid exposure, developmer.t of nodules (benign and malignant) and hypof inction, are dose dependent, the establishment of thyroid dose is most important in order to derive
dose-effect relationships. Unfortunately, it must be stated at the outset
that the thyroid dose estimates are subject to consideratle uncertainty and
may, at least in some cases, be considerably higher than estimated.
The effect of thyroid injury on growth and development in the children
is described in Section IV.
A.
Background (Chronology of Developments)
Beginning several years after e..posure it was noted that some children
exposed at <l10 years of age showed growth retardation, particularly boys exposed at <5 years of age (see Section IV), but the cause was not immediately
apparent.
It was recognized that thyroid hormone deficiency due to thyroid injury could result in such growth retardation, but examinations during this
early period did not reveal any thyroid abnormalities, and the PBI levels in
these children as well as in all Marshallese were in the normal to high range.
The growth retardation gradually became more apparent, and at 8 years post ex~
nosure two boys were recognized to be stunted in growth.
They had been ex-
posed at one year of age and gradually developed atrophy of the thyroid gland
and signs of myxedema with puffy faces, dry skin, sluggish reflexes, and bony
dysgenesis of the humerus and femur.
In 1965 a satisfactory method for serum thyroxine analysis by ion exchange column became available. Studies by this method showad that some of
the children did indeed have tow serum thyroxine levels. Control observations
on unexposed Marshallese revealed that many of them had unusually nigh
*The following persons assisted the senior author in the preparation of this
report or were actively involved in some of the special studies:
Surgical
rindings~—Dr. B. Dobyns (Cleveland Metropolitan General Hospital, Cleveland,
OH); Histopathology—-Dr. D.E. Paglia (U. of California, Los Angeles);
Hypothyroidism—-Dr. B.R. Larsen (Peter Bent Brigham Hospital, Boston, MA);
Clinical--Drs. J.B. Rall, J. Robbins, ard J. Wolff (NIH, Bethesda, MD); Dr.
J.T. Nicoloff (U. of Southern California, Los Angeles); Dr. B. Colcock (Lahey
Clinic, Boston, MA, Ret.); Drs. H. Pratt, K. Knudsen, and W. Adams (BNL);
Dr. C.S. Hill, Jr. (M.D. Anderson Hospital, Houston, TX); Or. D.D. Becker
(Cornell Medical Center, New York, NY).
- 53 -
See p. 55 for list of pathologists.