Cushing's Syndrome Overview
Cushing's syndrome is a disorder caused by prolonged exposure of the body's tissues to high levels of corticosteroids (glucocorticoids).
Corticosteroids are powerful steroid hormones produced by the adrenal glands, located above each kidney. They regulate the metabolism of proteins, carbohydrates, and fats. They reduce the immune system's inflammatory responses and help to maintain blood pressure and heart function. A vital function of corticosteroids is to help the body respond to stress.
Corticosteroid production by the adrenal glands follows a sequence of events. The hypothalamus (see Anatomy of the Endocrine System) releases corticotropin-releasing hormone (CRH), which causes the pituitary gland to secrete adrenocorticotropic hormone (ACTH), which in turn stimulates the adrenal glands to produce corticosteroid. When the corticosteroid level is low, more CRH and ACTH are produced; when the corticosteroid level is high, less CRH and ACTH are produced. Under normal conditions, the corticosteroid level and CRH/ACTH levels are in dynamic balance; Cushing's disease occurs when that balance is disturbed.
Excess corticosteroids have detrimental effects on many of the tissues and organs of the body. All of these effects together are called Cushing's syndrome.
Overproduction of corticosteroids can be caused by a tumor in the pituitary gland, which produces excess ACTH, thereby stimulating the adrenal gland to produce excess corticosteroids. This condition is called Cushing's disease because the origin is in the hypothalamic pituitary system. Cushing's syndrome is a qcollection of symptoms which look and act like Cushing's disease but is not the result of pituitary ACTH overproduction.
Endogenous Cushing's syndrome is the result of autonomous, unregulated production of corticosteroids by a tumor within one or both of the adrenal glands themselves. The most common cause of Cushing's syndrome, however, is exogenous Cushing's syndrome, which results from taking excessive amounts of corticosteroid drugs.
The majority of cases of Cushing's syndrome are caused by administration of corticosteroids (exogenous) for the treatment of long-term diseases such as asthma, arthritis, and lupus.
Medically Reviewed by a Doctor on 11/30/2015
George P Chrousos, MD, FAAP, MACP, MACE
Arthur B Chausmer, MD, PhD, FACP, FACE, FACN, CNS
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