And It's About Time There Was Some Support For Cushing's!
What Causes Cushing's Syndrome?
Cushing's syndrome occurs when the body's tissues are exposed to excessive levels of
cortisol for long periods of time. Many people suffer the symptoms of Cushing's syndrome because they take glucocorticoid
hormones such as prednisone for asthma, rheumatoid arthritis, lupus or other inflammatory diseases.
Others develop Cushing's syndrome because of overproduction of
cortisol
by the body. Normally, the production of cortisol
follows a precise chain of events. First, the hypothalamus, a part of the brain which is
about the size of a small sugar cube, sends corticotropin releasing hormone (CRH) to the
pituitary
gland.
CRH causes the pituitary
to secrete ACTH (adrenocorticotropin), a hormone that stimulates the
adrenal
glands. When the adrenals, which are located just above the kidneys, receive the
ACTH, they respond by releasing cortisol
into the bloodstream.
Cortisol performs vital tasks in the body. It helps maintain blood pressure and cardiovascular function,
reduces the immune system's inflammatory response, balances the effects of insulin in breaking down
sugar for energy, and regulates the metabolism of proteins, carbohydrates, and fats. One of
cortisol's most important jobs is to help the body respond to stress. For this reason, women in their last 3 months of
pregnancy and highly trained athletes normally have high levels of the hormone. People suffering from
depression, alcoholism, malnutrition and panic disorders also have increased
cortisol levels.
When the amount of cortisol
in the blood is adequate, the hypothalamus and pituitary
release less CRH and ACTH. This ensures that the amount of cortisol released by the adrenal glands is precisely balanced to
meet the body's daily needs. However, if something goes wrong with the adrenals or their regulating switches in the pituitary
gland or the hypothalamus, cortisol production can go awry.
Pituitary Adenoma Pituitary adenomas cause most cases of Cushing's syndrome. They are
benign, or non-cancerous, tumors
of the pituitary gland which secrete increased amounts of
ACTH. Most patients have a single adenoma.
This form of the syndrome, known as "Cushing's disease," affects women five times more frequently than
men.
Ectopic ACTH Syndrome
Some benign or malignant (cancerous) tumors
that arise outside the
pituitary
can produce
ACTH. This condition is known as ectopic ACTH syndrome. Lung tumors
cause over 50 percent of these cases. Men
are affected 3 times more frequently than women. The most common forms of ACTH-producing
tumors
are
oat cell, or small cell lung cancer, which accounts for about 25 percent of all lung cancer cases, and
carcinoid tumors. Other less common types of
tumors
that can produce ACTH are thymomas, pancreatic
islet cell tumors, and medullary carcinomas of the
thyroid.
Adrenocortical carcinomas, or
adrenal cancers, are the least common cause of
Cushing's syndrome. Cancer cells secrete excess levels of several
adrenal cortical hormones, including
cortisol and adrenal androgens. Adrenocortical carcinomas usually cause very high hormone levels and rapid development of
symptoms.
Familial Cushing's Syndrome
Most cases of Cushing's
syndrome are not inherited. Rarely, however, some individuals have special
causes of Cushing's syndrome due to an inherited tendency to develop
tumors
of one or more endocrine
glands.
In Primary Pigmented Micronodular Adrenal Disease, children or young adults develop small
cortisol-producing tumors
of the adrenal
glands.