While no cases have been diagnosed in a comparison population of unexposed Marshallese, Table 4 Serial thyroid-stimulating hormone* (TSH) the number of person years of observation is levels in two patients with pituitary tumors. small (698 person years for women 15-44 years of age, 1527 person years for the total population <45 years of age). This does not permit a meaningfulstatistical analysis of pituitary tumor incidence in the Marshall Islands. Nevertheless, the absence of cases in the unexposed group does tend to support the results of the statistical Case No. 1** analysis using data from Olmsted County. Note that the observation years of the Mar- | shallese cover the entire period from 1954 through 1982. No allowance is madein theincidence datafor any latent period in tumor induction because there is no available information on what that might be. Nevertheless, it is clear that both tumors were present 21-22 years after exposure. | The reason for the apparent increasein relative risk for pituitary tumors in the exposed Marshallese, if not chance occurrence, is unknown. There are noprior reportsof pituitary tumors being inducible by radiation in man, 110 1973 1974 1975 1976 1978 1.0 5.9 115t 1.8 1981 < 2.5 < 25 1.7 0.3 < 2.51 scanning. It should be noted that occult pituitary tumors can be foundin up to 27% of consecutive autopsies.*”*! It is not clear, however, that such ubiquitous neoplasmsare analogous to those which produceclinical disease. Prolactinoma Survey. The most common pituitary tumor in humansis prolactinoma,its in Japan or amongchildren whoreceived cran- chemical marker being hyperprolactinemia.”” In 1981-82 serum prolactin levels were obtained on 174 of the 178 persons remaining in the tain types of radiation can induce pituitary neo- plasia in man, thelink is not a strong one, being a exposed population (four persons have not been examined in several years). The prolactin radioimmunoassays were performed in the laboratory of Dr. P.R. Larsen, Peter Bent Brigham Hospital. One persistent and unexplained elevation was found in an 82-year-old womanin the Utirik group, who was 54 years of age at the time of exposureto fallout. It may be clinically pertinent that, although married, she had no children. Skull x rays revealed a normal sella turcica. Because 1) there was noclinical evidence of a mass lesion, 2) she was of an advancedage, and 3) the serum prolactin elevation was minimal (42 ng/ml, with the upper range of normal for females in this population, based on two standard deviations above the mean, being 22 ng/ml), further evaluation was not carried out. It is not certain, therefore, that statistical phenomenon without a knownbiologi- cal basis. Conceivably, pituitary neoplasia may have developed secondary to preexisting thyroid disease. Hyperplasia/adenoma formation of pituitary cells can result from thyroid hypofunction,°” and hypothyroidism is sometimes associated with hyperprolactinemia and/or galactorrhea.” Thyroid hypofunction has been noted amon 16% of the exposed individuals from Rongelap.” Hypothyroidism in general has not been associated with pituitary tumors in man, however, and the two Marshallese women were, for the most part, clinically and biochemically euthyroid en tested in the years preceding the pitta gmor diagnoses (see Table 4 for excep tionse 12 ae | 1972 t Year pituitary tumor was diagnosed. ial irradiation.“ While the development of two pituitary tumors in the relatively small population of exposed Marshallese maybe evidence thatcer- 4 1.0 1.7 * Normal values are jess than 5 » U/ml. ** Case No. 1 had a total thyroidectomy in 1969 for papillary carcinoma, and the elevated TSH levels in 1972 and 1976 were obtained when thyroxin was discontinued prior to 131] although they can be produced by external Cc? 2.2 1979 gamma radiation and apparently by boneseeking nuclides in experimental animals.” No increase in pituitary neoplasms has been noted among survivors of the atomic bombings cri 1965 1967 1969 Case No. 2