636:611.441:636.2 (571.61) ., ., , ., , ., ., , - . , . , . - . . Trush N.V., Doct.Bio.Sci., professor, Ivankina N.F., Doct.Bio.Sci., professor, Klejkova D.A., post-graduate student PHYSIOLOGICAL ACTIVITY OF THE THYROID GLAND OF LARGE HORNED LIVESTOCK IN IODINE DEFICIT ZONE BY YEAR SEASONS Changes in functional activity of a thyroid gland by seasons of the year reflects its morphological characteristic. Individual morphometric data of thyroid gland is more variable than changes by seasons of the year. During the autumn period morphometric parameters are higher than in spring. Quantitative definition of thyroxin level in blood of animals has diagnostic value at an estimation of a functional condition of a thyroid gland. Parameters of hormones in blood testify to functional activity of a thyroid gland in spring. , . , . , , - . - , , . [1, 2, 4]. , . [5] - - . . 4) - ), , [3]. - . - , , , - , , , , , . . - , Microsoft Exel. . . . , - 30 , . . , , . , - 4 - . - . - 4 ( ) . [1]. , 1 , , . - . , . - . 1 ) ) 10,08±0,515 0,04±0,01 7,70±0,709 0,02±0,01 , ( / 4) – . - , 0,03 % , . , : - , . - 100. - 4 , . 1. , , . - " . 18 - 19. 4. - : . . ", 2007. - , . 6. - . : / / // . 38-41. 2. , . . - 2000. - . , . 10. - 30 - 33. 5. . // . - 2006. - . 52. - , - . , , / . // - / , . . – 2006.- 8.- . 45-47. 3. , . . // , - . . .77-80. 31 . . – . // , 1984. -