Summary. A correlation was established between thyroid hormone levels, tumor tissue progression and thymus weight of experimental animals with an implanted color adenocarcinoma tumor (ACATOL). The study shows the role of thyroid hormones in the regulation of the proliferation of the expremental tumor of ACATOL and the activation of the immune system f the organism that has undergone a carcinogenic attack. 

Key words:  thymus involution, hypothyroidism, thyrotoxicosis, adenocarcinoma of the large intestine.

Summary: The article presents the findings of the morphological analysis of the regional lymph nodes showed that the activation of the immune defense of the body in response to the development of carcinogenesis is observed only in the simulation condition of hyperthyroidism and in tumor-bearing animals with no effects.

Keywords: AKATOL, carcinogenesis, hypothyroidism, hyperthyroidism, tumor, spleen, lymph nodes.