Influence of experimental hypothyroidism on the development of metastases in rats

The influence of experimental hypothyroidism induced by a synthetic antithyroid drug, methylthiouracil, upon the development of metastases was studied on male Wistar rats, inoculated intravenously with Walker 256 carcinosarcoma cells. The experimental results reveal obvious differences between the control group and the group previously treated with methylthiouracil, concerning the incidence, latent period, localization and tumor extension. Hypothyroidism promoted metastasis, increasing significantly the metastatic incidence (88% against 62% in controls), shortening the latent period and extending the localization of tumor metastases to unusual sites, such as liver and spinal column.