Hydrocortisone
Cortisol is a corticosteroid hormone that is involved in the response to stress; it increases blood pressure and blood sugar levels and suppresses the immune system. Synthetic cortisol, also known as hydrocortisone, is used as a drug mainly to fight allergies and inflammation. more...
Synthesis
 and some sex hormones (in the <i>zona reticulosa</i>), cortisol is its main secretion. (The name <i>cortisol</i> comes from <i>cortex</i>.)</p>
<p>The synthesis of cortisol in the adrenal gland is stimulated by the anterior lobe of the pituitary gland with adrenocorticotropic hormone (ACTH); production of ACTH is in turn stimulated by corticotropin releasing hormone (CRH), released by the hypothalamus.</p>
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<h2>Physiology</h2>
<p>The amount of cortisol present in the serum undergoes diurnal variation, with the highest levels present in the early morning, and lower levels in the evening, several hours after the onset of sleep. Information about the light/dark cycle is transmitted from the retina to the paired suprachiasmatic nuclei in the hypothalamus. Changed patterns of the serum cortisol levels have been observed in connection with abnormal ACTH levels, clinical depression, psychological stress, and such physiological stressors as hypoglycemia, illness, fever, trauma, surgery, fear, pain, physical exertion or extremes of temperature. There is also significant individual variation, although a given person tends to have consistent rhythms.</p>
<p>Cortisol also inhibits the secretion of corticotropin releasing hormone (CRH), resulting in feedback inhibition of ACTH secretion. Some researchers believe that this normal feedback system may break down when animals are exposed to chronic stress.</p>
<p>In normal release, cortisol has widespread actions which help restore homeostasis after stress. It acts as a physiological antagonist to insulin by promoting gluconeogenesis, breakdown of lipids, and proteins, and mobilization of extrahepatic amino acids and ketone bodies. This leads to increased blood glucose concentrations and increased glycogen formation in the liver (Freeman, 2002). It also increases blood pressure. In addition, immune and inflammatory cells have their responses to stress attenuated by cortisol, and the hormone thus lowers the activity of the immune system. Bone formation is also lowered by cortisol.</p>
<p>These normal endogenous functions are the basis for the physiological consequences of chronic stress - prolonged cortisol secretion causes muscle wastage, hyperglycemia, and suppresses immune / inflammatory responses. The same consequences arise from long-term use of glucocorticoid drugs.</p>
<p>Also, long-term exposure to cortisol results in damage to cells in the hippocampus. This damage results in impaired learning. However, short-term exposure of cortisol helps to create memories; this is the proposed mechanism for storage of flash bulb memories.</p>
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