High environmental temperature of 40 0С, applied in different developmental stages in White laboratory rat, is a stress on the body that load the adrenal glands. In terms of hypotermic stress adrenal glands work faster, producing increased amounts of adrenaline , noradrenaline and cortisol. In terms of long-term stress, and load of the glands are entering a phase of temporary hypofunction . If they are healthy, they hypertrophied trying to compensate for the reduced release of hormones. During a long and exhausting stress comes to chronic hypofunction of the adrenal glands