Study of thyroid status in newly calved cows with disorder of liver functio

Abstract

The article presents the results of a study of thyroid hormones - total triiodothyronine, total and free thyroxine in fresh cows at different ranges of bilirubin concentration in the blood. It was found that with an increase in the level of bilirubin, the functional activity of the thyroid gland decreases according to the principle of inverse relationship. It was found that the most sensitive marker to an increase in bilirubin is total T4. With a mild and moderate degree of hyperbilirubinemia, the level of this hormone decreases by 36.7-39.2%, with a pronounced increase in bilirubin in the blood, thyroxine decreases 3.6 times. With a slight increase in bilirubin in the blood, the level of T3 and fT4 decreases by 4.4-5.6%. With a more pronounced dysfunction of the liver, the degree of decrease in these hormones is much greater and is reliable. So, the concentration of T3 in groups decreases by 20.5-23.0%, and fT4 - by 33.4-40.0%. A decrease in the content of thyroid hormones in the blood against the background of hepatopathy is explained by a slowdown in all metabolic processes due to a decrease in the functional activity of the liver. The reason for the hypofunction of the thyroid gland is the lack of the need for the amount of hormones that is produced in the body of a healthy animal. Against the background of hepatopathy, the homeostasis of triiodothyronine, as the most important metabolically active thyroid hormone, is maximally maintained. At the same time, a decrease in the rate of catabolism of hormones in the liver does not contribute to a change in their concentration in the blood, since the half-life of T4 is much higher than T3, therefore it is the decrease in the rate of their synthesis in the gland and secretion into the blood that matters.