Cortisol

Cortisol is a hormone, related to the steroids, produced in the adrenal gland. It increases blood pressure and blood sugar levels, aids the metabolism of food, and suppresses the immune system and bone production. In a growing fetus, it aids development of the lungs. 
Too little cortisol results in Addison's disease whilst too much cortisol results in Cushing's syndrome. In a normal physiology, cortisol levels follow a daily rhythm, peaking in the morning and trailing during sleep. This pattern can be interrupted by several disorders, such as clinical depression, stress, hypoglycemia, fever and pain.
In addition to the treatment of Addison's, a pharmaceutical preparation of cortisol is used to treat arthritis and allergy.
In the body, cortisol will counteract the effect of insulin, slowing the uptake of glucose into cells. However, it also has the effect of boosting the liver production of glucose from other sugars. It also increases the production of stomach acid, inhibits the loss of sodium in the small intestine, and increases the production of urine. It also increase the effect of adrenaline and norepinephrine.
Hydrocortisone(TM) is the pharmaceutical preparation of cortisol
Cortisol at WikipediaCortisol