Influence of thyroid secretion on the in­duction of leukemia in Dba mice by methylcholanthrene

1) The influence of thyroid secretion upon the induction of leukemia in Dba/2 male mice by methylcholanthrene was investigated. Radiothyroidectomy significantly reduced the incidence of leukemia in these mice. This reduction in incidence did not occur if radiothyroidectomy was performed after the administration of the carcinogen. 2) Data indicated that hypothyroidism following radiothyroidectomy interfered with the initiation rather than the promotion of methylcholanthrene- induced-Ieukemogenesis. 3) No correlation between incidence of leukemia and body weights in the mice was noted.