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Cushing's Syndrome - Part One...

15 Oct 1999 Featured Article by Troya Renee Yoder, used with permission as originally posted on Suite, Pituitary Disorders

What is Cushing's Syndrome?

First described by the physician, Harvey Cushing, in 1912, Cushing’s syndrome (sometimes called hypercortisolism) refers to a disorder in which the body suffers from prolonged exposure to high levels of the stress hormone, cortisol. Because of the gradual nature of the disease, the time between the onset of symptoms and the diagnosis of Cushing’s is often long and frustrating.

The Cortisol Production Pathway

In order to understand how Cushing’s syndrome arises, it is necessary to briefly examine the cortisol pathway. First, the hypothalamus secretes corticotropin releasing hormone (CRH). CRH stimulates the pituitary gland to secrete ACTH, which causes the adrenal glands to release cortisol into the bloodstream. A biologic feedback loop exists in which the hypothalamus and pituitary release less CRH and ACTH when cortisol reaches adequate levels in the bloodstream. However, there are a number of situations that may upset the cortisol feedback loop, leading to excess cortisol secretion, and hence, Cushing’s syndrome.

What are the Symptoms of Cushing’s Syndrome?

The symptoms of Cushing’s are many, and no two patients are affected the same. Some of the most common include:

What Causes Cushing’s Syndrome?

There are four different possible causes of Cushing’s: a pituitary tumor, an adrenal tumor, a tumor outside the pituitary or adrenal glands, and exposure to certain medications. It is very important to determine the source of Cushing’s (Part 2 in this series will address laboratory tests used to differentiate between the possible causes of Cushing’s).

  1. Pituitary Adenomas

    The most common cause of Cushing’s is a benign pituitary tumor, which secretes adrenocorticotrophic hormone (ACTH). This type of Cushing’s is called “Cushing’s Disease” and is five times more common in women than men.

  2. Adrenal Tumors

    15% of all cases of Cushing’s syndrome are caused by cortisol-secreting tumor of the adrenal gland. 6 out of 1,000,000 people affected.

  3. Ectopic Cushing’s Syndrome

    Some benign or cancerous tumors outside of the pituitary and adrenal glands secrete excess ACTH, causing Ectopic Cushing’s syndrome. The most common types of tumors are oat cell tumors of the lung, thymomas, pancreatic islet cell tumors and medullary carcinomas of the thyroid. Ectopic Cushing’s syndrome occurs in 1 out of 100,000 people and is three times more common in men than women.

  4. Exogenous Cushing’s Syndrome

    The treatment of other diseases such as asthma and rheumatoid arthritis with glucocorticoid hormones can cause exogenous Cushing’s syndrome, or Cushing’s syndrome-like symptoms.

What is Pseudo Cushing’s?

Pseudo Cushing’s describes conditions such as depression, alcoholism, severe stress, and panic disorders that may cause some of the symptoms and altered laboratory findings of consistent with Cushing’s syndrome.




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