cctumy in the rat has been reported to cause adenoma formation in the remaining thyroid tssue 2 vears later.” All these procedures produce hypothyroidism which serves as an effective stimulant to the secretion of TSH by the pituitary gland. The thyroid gland un‘der the influence ofTSH first undergoes diffuse hyperplasia and hyper- trophy and adenoma formation. In the cases of iodine deficiency and partial thyroidectomy, it is probable that no drug or carcinogenic agent is in- volved The incidence of carcinomas after a combinationof carcinogenic agents (such as radiation or acety laminofluorene) and any factor that causes hypothyroidism is much higher. '* Radiation by cither x rays or '"'T is particularly effective, since it simultaneously acts as a carcinogen and, by im- Urine analyses indicate that iodine intake is adequate. The incidence of nodules and sporadi cases of goiter seen at the Majuro Hospital* is low, and the Marshallese population shows no evidence for goitrogenic factors in their environment. The sensitivity of children’s thyroid glands to the development of neoplastic changes from radia lion exposure has been amply demonstrated. A series of retrospective and prospective studies haye clearly shown the causal relation of irradiation of the neck region in infants and later development of thyroid cancer." ** Although the calculation of the dosage in the Marshallese is subject to large uncertainties, the greater incidence of patholovical changes in the glands of the Marshallese maybe to the relative magnitudes of the radiation doses received, the small child’s gland probably having related to a greater dose of radiation received by their thyroid glands. Lesions similar to those seen in the Marshallese have been reported in children 3 to Il vears old after treatment with '''T for thyrotoxicosis.” "' Doniach”’ points out that cell division in the growing thyroid gland of the child maybe a factor in the increased sensitivity to iradiation. There appears to be an increased 1n¢1dence of thyroid carcinomain inhabitants of Hiroshima ar.d Nagasaki exposed to radiation from the atomic bomb explosions."" These people were exposed to varying doses of external radiation to the thyroid gland but not to internal exposure from radioiodine. It has been assumedthat the slight growth re- by the adult's gland. Since most of these lesions children was due io radiation, but the mechanism pairing the functional capacity of the gland, induces USH secretion and thyroid stimulation. The high incidence of adenomatous goiters and hypothyroidism in the more heavily irradiated children exposed at < LO vears of age. compared with no abnormalies in some 100 children in the same age range in the less exposed and unexposed groups, leaves litle doubt about the etiological re- lationship of these lesions with irradiation exposare. Phe higher incidence tn children may be re- lated to increased sensitivity of the child’s thyroid to irradiation but is probably related moredirectly received 3 to 10 times the radiation dose received appeared in teen-age children, puberty may have been a contributing factor. The incidence of the lesions in female children is onlyslightly greater than in taale children (1.27 to Lj). A greater prev- alence of thyroid abnormalities in that sex ts correctly noted. The increased incidence of thyroid abnormalities, including one cose of malignancy. tu the adults of the more heavily exposed Ronge- 2p population makes i necessary to consider seriously radiation exposure as the etiological factor. in. opendis 7 statistics on thyroid malignancies inthe Marshall Islancs and the Trust Territory are presented. A low incidence of solitary nodules was noted in older (>> 50 veats of age) unexposed Morshatlese of both Rongciap and Utirik Islands. tardation previously noted in someof the exposed has been obscure. The growth hormone studies suggested that pituitary function was normal. X rays of the sella turcica showed no evidence of pituitary abnormality. With the recent developinent of hypothyroidism in two of the most growthretarded boys and evidence of mild hypothyroidism in several other children with thyroid nodules and growth retardation, a hypothyroid etiology seems most likely. Elevated TSH levels indicate that the hypothyroidism is primary. Minimal hypotunction of the gland may have been missed in the past, since the apparently norma! PBI levcls mayhave been spuriously high, the true thyroxine level being masked bythe elevated iodoprotein component characteristic of the Marshaliese ‘Phe snide nodule case in the less exposed to-vear- old Ndingnae woman, on the other hand, may well tallinto the category of the sporadic type, since the nodule was well cacapsulated, and the remainder of the the raid gland appeared pormal, “In Maret. 1966. two cases of goiter with large, nodubir lands were seen at the Majuro Hospital One mas hase had mind ts pertivtordism “These cases were not part of tne population under studs