Information on the content of the natural stable element iodine (127 I) in the radioactively contaminated territories of Ukrainian Polissia and the impact of its lack in these regions on the physiological indicators of the health of cattle (cattle) were analyzed. It is known that the most polluted territories of Ukraine belong to the Polissia zone, which are characterized as zones with a deficiency of biogenic trace elements in the soil, including iodine. It is also well known that it is radioactive iodine that plays a leading role in the radiation damage to biological objects in almost any nuclear accident when nuclear fission products enter the environment. Chernobyl NPP. Diagnostic signs and the clinical picture of radiation damage to animals by radioactive iodine are quite well described in the scientific literature. However, in our opinion, insufficient attention has been paid to these issues in situations where radioactive iodine affects animal populations in provinces endemic for stable iodine. It is known from the literature that the main clinical picture of stable iodine deficiency in cattle is: short stature, low weight, low productivity, characteristic changes in the hair coat - curliness, long hair, wrinkled skin, bradycardia, hypotonia of the scar, impaired reproductive functions, impaired erythro- and leukopoiesis. But when assessing the state of health of cattle in radioactively contaminated territories during the acute period of development of the Chernobyl accident, researchers noted very similar signs. In active experiments with the artificial introduction of radioactive iodine (131 I) into the body of cattle of various ages, we investigated changes in the physiological state of animals under the influence of various formed doses of radiation of the thyroid gland and confirmed our hypothesis regarding the similarity of the biological effects of radioiodine damage and the clinical picture of stable iodine deficiency . That is, screening of the main physiological parameters of animal health is the key to correct assessments of the degree of damage to the animal organism by radioactive iodine isotopes.