Factors Influencing Development of Hypophyseal Tumors in Mice After Treatment with Radioactive Iodine.

Abstract

Thyroid glands of mice of the C57 BL strain are destroyed by injns. of 200 [mu]c of I131. Fatal tumors of the anterior pituitary develop about 1 yr. after the radiothyroidectomy. If mice are fed the Remington "low-iodine" diet the same thyroidal destruction is achieved by 30 [mu]c of I131. Mice radiothyroidectomized by 30 [mu]c of I131 do not develop hypophyseal tumors. Two injns. of thyroxine per wk. of 2.5 [mu]g. each almost completely prevented the development of the hypo-physeal tumors after 200 [mu]c of I131. Implants of new thyroidal tissue completely prevented development of the tumors. Implants of pituitary, ovary, or adrenal were without ability to inhibit growth of the pituitary tumor. It is concluded that the radiothyroidectomy is necessary for growth of the hypophyseal tumor, but another factor or factors are also involved in the phenomenon.