Cortisol is a hormone that is produced by the adrenal gland.

The important functions of cortisol include:

• Assisting the body in its response to stress
• Carbohydrate and fat metabolism
• Helping balance the effects of insulin in breaking down sugar for energy
• Helping the immune system's response
• Maintaining blood pressure
• Regulation of protein

Causes of Cushing's syndrome include:

• Treatment with steroid medications that have the same effects as cortisone, such as:
• Prednisone
• Medrol
• Dexamethasone
• Hydrocortisone
• Tumors that produce a hormone that stimulates the adrenal glands to make excess cortisol:
• Pituitary tumor
• Small cell carcinoma of the lung
• Bronchial carcinoid tumor