[Comparative biological effectiveness of 125I and 131I]

An experimental study of comparative biological efficacy of 125I and 131I at equal absorbed doses (2.3 and 13 Gy) in the thyroid of rats showed that the blastomogenic effect of both radionuclides was almost the same. Sex differences were found in the development of long-term consequences (20 mos. after drug administration): breast tumors developed in female rats and thyroid tumors in male rats.