_ in the older group appears to be in line with this reasoning. The cases of two stunted Marshallese boys who showed almost complete atrophy of their thyroid glands with no evidence of nodular development are probably comparable to those cases of hypothyroidism developing in patients years after receiving radioactive iodine therapy. It should be pointed out that the thyroid exposures in the Rongelapese were slightly different from patients treated with '*'I because their thyroids were not hyperplastic when exposed and at least part of the radioactive iodine isotopes to which © they were exposed were of shorter half life than '*'I. In addition their exposure was complicated by gamma radiation. There were some factors secondary to radiation exposure’ that might have enhanced the develop- ment of thyroid lesions in the Marshallese. Iodine deficiency or presence of goitrogens in the diet did not appear to be among these. However, the physiological stresses. of puberty and pregnancy may have played a role in the development of the lesions. For instance the development of ten cases of nodular goiter in the children during or near the time of puberty might indicate that this stress may have enhanced nodular development. In three women who developed thyroid nodules later the demand of multiple pregnancies may have been related. However, since the latent period between exposure and nodule discovery varied only between 10 and 13 years it may be argued that development of thyroid nodules was independent of these stresses. On the other hand it is noteworthy that all of the women who developed malignant thyroid lesions had multiple pregnancies prior to the appearance of such neoplasms. The development of thyroid nodules in the Marshallese showed only a slight preponderance in favor 324 of the women (1.3 to 1.0). This is similar to the near equal sex ratio reported by Toyooka et al’* for thyroid nodules developing in persons irradiated over the neck region in infancy. However, in the case of carcinoma of the thyroid the expected female preponderance occurred.* The insidious development of growth retardation in some of the Marshallese children before clinical evidence of thyroid abnormality or deficiency was recognized demonstrates the apparent sensitivity of growth and developmental proces- ses to borderline or subclinical thy- Med 66:1214-1242, 1967. 3. Sutow WW, Conard RA, Griffith KM: Growth status of children exposed to fallout radiation on Marshall Islands. Pedtatrics 36:721-731, 1965, 4 Rall JE, Conard RA: Elevation of serum protein-bound iodine level in inhabitants of Marshall Islands. Amer J Med 40:883-886, 1966. & Sloan LW, Frantz VK: Thyroid can- cer: Clinical aspects, In Werner SC (ed): The Thyroid, ed 2. New York, Harper & Row, Publishers Inc, 1962, pp 445-468. 6. Maloof F, Dobyns BM, Vicery A: The effects of various doses of radioactive iodine on the function and structure of the thyroid of the rat. Endocrinology 50:612- 638, 1952. 7. Doniach I: Comparison of carcinogenic effect of x-irradiation with radioactive iodine on rat's thyroid. Brit J Cancer 11:67-76, 1957. roid deficiency. All possible steps 8. Lindsay S, Chaikoff IL: Effects of irradiation on thyroid gland with particular are being taken so that the children reference to induction of thyroid neowill adhere to the present thyroid plasias: Review. Cancer Res 24:1099-1107. treatment schedule so that they will 1964. 9. Sheline GE, Lindsay S, McCormack achieve satisfactory growth and . KR, et al: Thyroid nodules occurring late maturation. after treatment of thyrotoxicosis with radioCareful medical surveillance of iodine. J Clin Endocr 22:3-18, 1962. 10. Hollingsworth DR, Hamilton HB. these exposed people including Tamagaki H, et al: Thyroid disease: A those on Utirik will be essential in study in Hiroshima, Japan. Medicine 42: future years. The latent period for 47-71, 1963. 1L Pincus RA, Reichlin S, Hempe!the development of cancer was 7 mann LH: Thyreid abnormalities after years in one case and 14 and 15 radiation exposure in infancy. Anan Intern years in the other two. The fact Med @8:1154-1164, 1967. 12. Tayooka ET, Pifer JW, Hempelthat there may be a longer latent mann LH: Neoplasms in children treated period for the induction of maligwith x-rays for thymic enlargement: III. nant change is borne out by a reClinical description of cases. J Nat Cancer Inat 31:1379-1405, 1963. port by Goolden who noted the 13. Hempelmann LH: Risk of thyroid development of thyroid cancer 40 deoplaams after irradiation in childhood. years after radiation exposure.** It Science 160:159-163, 1969. 14 Silver S: Radioactive Isotopes in may be that we are just reaching Medicine and Biology, ed 2. Philadelphia. the critical period in the postradiaLea & Febiger, 1962, pp 138-148. tion observations. 1& Upton AC: The dose-response relation im radiation-induced cancer. Cancer This investigation was supported by the US Atomic Energy Commission. Keith Thompson, MS, assisted in carrying out statistical analyses. CAPT Carl A. Broaddus, Jr., MC, USN; Bentley P. Colcock, MD; and Brown M. Dobyns, MD, performed the thyroid operations. References 1. Conard RA, Rall JE, Sutow WW: Thyroid nodules as a late sequela of radioactive fallout in a Marshal] Island population exposed in 1954. New Eng J Med 274: 1392-1399, 1966. 2. Robbins J, Rall JE, Conard RA: Late effect of radioactive iodine in fallout: Combined clinical staff conference at the Na- JAMA, Oct 12, 1970 # Volt 214, No 2 9017814 tional Institutes of Health. Ann intern Printed and Published in the United States of America Res 21:717-729, 1961. 16 Shellabarger CJ, Bond VP, Cronkite EP: Studies on radiation-induced mammary gland neoplasia in the rat: VII. The effects of fractionation and protraction of sublethal total-body irradiaton. Radiat Res 17:101-169, 1962. 17. Marks S, Bustad LK: Thyroid neoplasms in sheep fed radioiodine. J Nat Caneer Inst 30:661-673, 1963. 18 Goolden AWG: Carcinoma of the thyraid following irradiation. Brit Med J 2:954-965, 1958. . Thyroid Neopiasia—Conard et al