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

Abstract

Summary

1. Radiation thyroidectomy (under specified dietary conditions) with smaller amounts of I¹³¹ is not followed by pituitary tumors in C₅₇ mice. 2. Such radiation thyroidectomy with larger quantities of I¹³¹ is followed by pituitary tumors. 3. Thyroid implants or adequate thyroxine dosages prevent appearance of the pituitary tumors after suitable I¹³¹ treatment. 4. Similar implantation of pituitary, ovarian, or adrenal tissue in treated mice does not prevent growth of the tumor. It is concluded that the radiation thyroidectomy is a necessary, but not the sole factor, leading to growth of the pituitary tumor in I¹³¹-treated mice. It appears likely that another factor, related to the ionizing radiation itself, may be an influence aggravating or synergizing the thyroidectomy in its tumorigenic action on the pituitary gland of the mouse.