[Behavior of thyroid hormones, corticosterone, adrenocorticotropic hormone and insulin in the plasma of the rat under stress conditions].

In male Wistar rats the behaviour of the plasma concentrations of thyroid hormones, corticosterone, adrenocorticotrophic hormone and insulin was examined in the course of a hypokinase stress of 6 weeks duration. Blood was taken after a stress of 1, 3 and 6 weeks. In these cases in thyroid hormones a decrease of the thyroxine (T4) and an increase of the triiodothyronine (T3) appeared. In an increased need of energy of the organism apparently a more rapid peripheral conversion of T4 to the more active metabolic T3 takes place. Only after a longer stress the deficit of thyroid hormone is equalized via the regulating circle hypothalamus-hypophysis-thyroid gland. The hormones ACTH and corticosterone which are connected together in the regulation system hypothalamus-hypophysis-adrenal cortex, after one week slightly increase in the plasma of rats and clearly decrease after a stress of 3 weeks. This shows that in a longer stress load apparently an exhaustion of the bioenergetic reserves of the organism develops. At last under long-term stress a significant decrease of the plasma insulin level was found. The decrease of insulin might be conditioned by an endogenic liberation of catecholamine.