[Development of a transplantable mammary gland cancer in rats at different thyroid hormone levels].

In experiments on female rats of various age the authors studied the effect of thyroid hormones on the growth of the mammary gland transplantable cancer. In young animals the percentage of spontaneous tumor regression and the survival were found to increase with age, synchronously with a rise in blood thyroxine level. Injection of thyroxine in a dose of 5 mkg into 2-month old animals induces marked inhibition of the growth, and in later terms a complete tumor regression in 78% of cases. In thyroidectomized rats a rapid tumor growth was terminated by death in all animals of this series. It is the authors' opinion that thyroid hormones stimulate the transplantation immunity, correct the functioning of the hypothalamo-hypophyseal-genital system.