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They influence the energy metabolism of most body cells and help us to resist stressors.
NORMAL Circumstances - they help body adapt to intermittent food intake by keeping blood glucose levels fairly constant, and maintain blood pressure by increasing the action of vasocontrictors.
STRESS - due to hemorrhage, infection or physical/emotional trauma evokes a higher output of glucocorticoids which helps the body negotiate crisis.
Glucocorticoid hormones include corisol (hydrocortisone), cortisone, and corticosterone, but only cortisol is secreted in significant amounts in humans.
Basic Mechanism of glucocorticoid action is to modify gene activity. Glucocorticoid secretion is regulated by negative feedback. Cortisol is released by ACTH, triggered by hypothalamus releasing CRH. Rising cortisol levels feed back to act on both the hypothalamus and the anterior pituitary, preventing CRH release and shutting off ACTH and cortisol secretion. Cortisol secretory bursts, driven by patterns of eating and activity, occur in a definite pattern throughout the day & night.
Normal cortisol rhythm is interrupted by acute stress as CNS centers override the inhibitory effects of elevated cortisol levels and trigger CRH release. The increase in ACTH blood levels causes an outpouring of cortisol from the adrenal cortex. Stress results in a dramatic rise in blood levels of glucose, fatty acids, and amino acids, all provoked by cortisol. Cortisol's prime metaboic effect is to provoke gluconeogenesis, the formation of glucose from fats and proteins. Cortisol mobilizes fatty acids from adipose tissue and encourages their increased use for energy to save glucose for the brain. Under cortisol's influence, stored proteins are broken down to provide building blocks for repair or for making enzymes to be used in metabolic process. Cortisol enhances the sympathetic nervous system's vasoconstrictive effects, and the rise in blood pressure and circulatory efficiency that results helps ensure that these nutrients are quickly distributed to the cells.
Cortisol excess is associated with significant ant-inflammatory and anti-immune effects.
Excessive levels of glucocorticoids:
1. Depress cartilage and bone formation
2. Inhibit inflammation by deceasing the release of inflammatory chemicals.
3. Depress the immune system
4. Promote changes in cardiovascular, neural and gastrointestinal function.
Glucocorticoid drugs control symptoms of many chronic inflammatory disorders, such as rheumatoid arthritis or allergic responses. Although they relieve some of the symptoms of these disorders, they also cause the undesirable effects of excessive levels of these hormones.