Abstract
The results of studies of morphological changes in the thyroid gland and the functional state of the organism of clinically healthy dogs living in the III zone of radioactive contamination (III RCZ) after a man-made accident at a nuclear power plant are presented. The aim of the work is to study the effect of prolonged radioactive radiation of caesium–137 radionuclides on changes in the morphofunctional state of the thyroid gland. Clinical, hematological, biochemical and pathomorphological studies of animals were carried out, the degree of radioactive contamination of water, feed, the background of the environment, the specific activity of gamma radiation of thyroid tissues were studied. The radiological indicators of the III zone of radioactive contamination are 3 times higher in terms of the power of the exposure dose of radiation and 6.8 times higher in terms of the specific activity of the diet and thyroid tissues. Abnormalities of adequate metabolism and functional activity of different systems were found in clinically healthy dogs. Signs of hypothyroidism were clinically identified in 28% of dogs. Laboratory studies have established hypochromic anemia, leucopenia, hypoalbuminemia, bilirubinemia, aspartate aminotransferase hyperfermentation, creatininemia, uremia, and cholesterolemia. In the hormonal profile, the level of triiodothyronine, thyroxine and thyroid-stimulating hormone was significantly reduced, which indicates the development of secondary hypothyroidism under the influence of caesium-137. Pathomorphological studies have determined hyperplasia of the organ, degenerative processes in functional structures – follicles, desquamation and degradation of thyrocytes, hemorrhages in the interfollicular tissue, which is the morphological equivalent of hypothyroidism.
https://ror.org/044tay155 
