Influence of thyroid secretion on the in-duction 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 methylcholanthreneinduced-Ieukemogenesis. 3) No correlation between incidence of leukemia and body weights in the mice was noted. ∗Copyright c ©OKAYAMA UNIVERSITY MEDICAL SCHOOL Acta Med. Okayama 14, 14-21 (1959) INFLUENCE OF THYROID SECRETION ON THE INDUCTION OF LEUKEMIA IN Dba MICE BY METHYLCHOLANTHRENE Nobuo ODA* and Noriaki IDA The University of Texas, M. D. Anderson Hospital and Tumor Institute Texas, U. S. A. (Director: Dr. A. Kirschbaum) Received for publication, Nov. 10, 1959 There has long been speculation regarding a possible relationship between hematopoietic tissues and thyroid function. Lymphocytosis has often been noted in patients with hyperthyroidism. Growth of lymphatic tissues in thyroxine-treated animals has been demonstrated. Elevation of metabolic rates has been observed in patients with leukemia. Blood iodine can be markedly elevated in the lymphoid leukemia patient. Striking remission after thyroidectomy has been reported in a patient with chronic lymphocytic leukemia. GRAD (1955)1.2 investigated the influence of hyper· and hypothyroidism upon the incidence of mouse leukemia. He found that thyroxine decreased and thiouracil increased the incidence of spontaneous leukemia in AKR mice. In 1953, BIELSCHOWSKy3 reported his studies of tumor induction with 2-aminofluorene and its acetyl-derivatives in thyroidectomized rats. In his experiment, the incidence of liver tumors was suppressed by thyroidectomy performed prior to the administration of carcinogen. No suppressive effect was found when thyroidectomy was done after the administration of carcinogen. WOLFSON (1956)4 demonstrated that thyroidectomy by radioactive iodine shortened the interval between the onset of sarcoma and the administration of methylcholanthrene to rats. Since these results appeared to show some discrepancies, the present investigations were undertaken to evaluate the influence of hypothyroidism upon leukemogenesis in mice. In our experiment, Dba/2 male mice were used as the experimental animal, methylcholanthrene as the carcinogen, and radioiodine as the proc~dure of thyroidectomy. * Present address: Department of Pediatrics, Okayama University Medical school, Okayama, Japan