Effects of Glucocorticoids on Circulating Concentrations of Thyroxine (T₄) and Triiodothyronine (T₃) and on Peripheral Monodeiodination in Pre- and Post-Hatching Chickens

Abstract

The administration of either glucocorticoids (dexamethasone or corticosterone) or adrenocorticotropic hormone (ACTH) to chicken embryos was followed by increase in the circulating concentration of triiodothyronine (T3), the T3 to thyroxine (T4) ratio and the activity of liver T4-5' monodeiodinase. No consistent changes in plasma concentrations of T4 or GH were observed. In post-hatching chicks, corticosterone and dexamethasone depressed the circulating concentrations of both T4 and T3. Iopanoc acid, an inhibitor of liver T4-5' monodeiodinase, elevated plasma concentrations of T4 and depressed those of T3 in both chicken embryos and young chicks. It is suggested that glucocorticoids affect circulating concentrations of T4 and T3 both by affecting the activity of the liver T4-5' monodeiodinase and by influencing the hypothalamo-pituitary axis.

Effects of glucose oxidase on the growth performance, serum parameters and faecal microflora of piglets

“…Triiodothyronine and thyroxine are tyrosine-based hormones produced by the thyroid gland, and plasma T 4 can be converted into T 3 (Sterling et al, 1970). Thyroid hormones have profound effects on important physiological processes such as development and growth (Visser, 1990;Namroud et al, 2010) and regulation of metabolism (Decuypere et al, 1983;. Another key factor is GH, which mainly stimulates growth, cell reproduction and regeneration (Sorensen et al, 1992).…”

“…For example, triiodothyronine (T 3 ) and thyroxine (T 4 ) are tyrosine-based hormones produced by the thyroid gland, which are primarily responsible for regulation of the pig's metabolism (Decuypere et al, 1983;. However, no experiment has been designed to evaluate the interrelationships between blood constituent changes and GOD.…”

Effect of chronic hypoxia during embryonic development on physiological functioning and on hatching and post-hatching parameters related to ascites syndrome in broiler chickens

“…This was confirmed by the results of Buys et al (1998) showing a concomitant higher activity of thyroid hormones, earlier pipping and hatching of high CO 2 -incubated embryos compared with the normal CO 2 -incubated embryos. On the other hand, Decuypere et al (1983) and Meeuwis et al (1989) demonstrated that corticosterone is required for peripheral conversion of T 4 to T 3 during the prenatal life. Thus, the higher corticosterone levels in high-altitude-incubated eggs might have served to boost the shift in T 3 /T 4 ratio.…”

“…Early hatching at 482 h of incubation, final hatching at 508 h of incubation, embryonic mortality and non-fertile eggs were recorded. Blood samples were collected in heparinized tubes from 30 embryos per incubator by cardiac puncture at the non-external pipping stage (460 h of incubation) and in newly hatched chicks for determination of plasma thyroid (T 3 , T 4 ), corticosterone and lactic acid levels as described earlier (Decuypere et al ., 1983(Decuypere et al ., , 1994Meeuwis et al ., 1989;Hassanzadeh et al ., 1997). Plasma lactic acid was measured using Sigma kits 826 (Sigma, St Louis, MO, USA).…”

Thyroid hormone level and relative liver weight in male turkeys in relationship with their welfare

“…The aggressiveness on its turn causes stress, indicated by the increased plasma corticosterone level (Rushen, 1996;Popova -Ralcheva et al, 2002-а;Popova -Ralcheva et al, 2002-б.). Decuypere et al (1983) suggested that corticosterone can affect circulating triiodothyronine and thyroxine by altering the activity of liver T4-5 monodeiodinase and by influencing the hypothalamo-hypophysealpituitary axis involved in thyrotrophin-stimulating hormone secretion. Thus, increases in plasma corticosterone levels and plasma thyroxine levels in poults are most likely related to the adaptation to changes in metabolic demands caused by physiological stress (Guzmán et al, 2000;Davis et al, 2000;Decuypere and Kuhn, 1988).…”