. ae te ot Saal 1 a 2 ” @- ‘ a aS eee”ee ee mm ee ee; 40 “T ae qT T KC! O4 + aaa — a ? Ss ~t J NECK UPTAKE (%) 3 T 20 \~-,—4 rn “oN sage" ° i j a l L “HOURS Figure 30. Neck accumulation of '*?I in subjects with thy- roid abnormality. Values are gross neck counts as % of dose, uncorrected for blood backgroundfollowing oral ad- ministration of '??I. Computer analysis of these data indicates that 7% of the extrathyroidal iodide poolis “‘seen”’ by the neck counter. At the vertical lines, 500 mg KCIO, was given by mouth. 4, Subject No. 54; m, subject No. 2 (partial thyroidectomy); 0, subject No. 65; @, subject No. 3; O, subject No. 3; a, subject No. 69 (partial thyroidectomy). and 20) had little or no response to TSH. The other patients had apparently normalthyroid accumulation rates, and several (Nos. 33, 42, 59, 61, 64, and 65) responded to TSH. Urine excretion rates were variable and, in someinstances, very low, probably because of incomplete urinecollection. Following TSH,in manyinstancesthe urine excretion rate was lower than the control. The reason for this is unknown. Thetheoretical thyroid fraction following TSH was sometimes elevated despite a fall in thyroid accumulation rate because of a relatively greaterfall in urine excretion rate. Incomplete urine collection probably accounts for the very high thyroid fraction in some cases. The thyroid accumulation rate, on the other hand, is relatively unaffected by inaccurate urine collection. From the data in Tables 20 and 21 it is evident that several of the children who developed thyroid nodules but were notclinically hypothyroid had evidence thattheir thyroid glands were stimulated by elevated endogenous TSH production, and two of these children were unable to respond furtherto exogenous TSH. Results of Thyroid Hormone Therapy Althoughit is too soon to evaluate completely the results of thyroid hormonetreatment, there are definite indications of beneficial effects. In one 30083245 adult a nodule could not be palpated 6 months after treatment was begun. In September 1966, thyroid examinations showedthat 4 children with nodules (Nos. 19, 36, 54, and 72) noted previously had evidence of slight regression of the nodules, and it was decided to re-evaluate their cases in March1967, after another 6 monthsof therapy. The curves for stature and bone age before and after thyroid hormone administration, plotted for the two most retarded boys (Nos. 3 and 5) in Figure 31, show a definite spurt in growth subsequent to treatment. This acceleration is very prominent for bone developmentin subject No. 3. Figure 32A shows the remarkable change in appearance of No. 3 after thyroid hormonetherapy for 6 months. Figure 32B shows the improvement in bone maturation in wrist bones of No. 3 after 1 year of ther- apy — compare with Figure 28. These findings — indicate that the growth retardation noted among the boys wasattributable to functional hypothyroidism. Supporting this assumptionis the appearance of epiphyseal dysgenesis in one of these children. Figure 29 showsthis dysgenesis in the heads of the humeri. Until 1965, the serum proteinbound iodine (PBI) determinations had yielded results in the euthyroid range. It is possible, however, that the PBI levels actually represented disproportionately high amounts of physiologically | inactive serum iodoprotein and inadequate amounts of active hormone. The forthcomingsurvey in 1967 will be importantin assessing further growth stimulation from thyroid hormone treatment. Discussion of Thyroid Findings The development of abnormalities of the thyroid glands in the exposed Marshallese people beginning 9 years after fallout is consistent with the knownetiological relationship of irradiation of the thyroid gland with the developmentof such abnormalities. Though the exact mechanism involved in the pathogenesis of such lesionsts not clear, it is known that adenomasand cancers of the thyroid gland can be produced in laboratory animals by a variety of agents or regimens which interfere with the ability of the gland to synthesize thyroid hormone. Both benign and malignant neoplasms have been shown to be produced byiodine defictency,** agents that chemically inhibit thyroxine synthesis such as thiouracil,’*"*" x irradia- uon of the gland, °° ** andirradiation of the gland with ‘'#'T.$45* Furthermore, subtotal thvroid-