Cushing syndrome consists of the physical and mental changes that result from having too much cortisol in the blood for a long period of time. Cortisol is a steroid hormone produced by the adrenal glands, located above the kidneys. In normal amounts, cortisol helps the body:
There are two types of Cushing syndrome: exogenous (caused by factors outside the body) and endogenous (caused by factors within the body). The symptoms for both are the same. The only difference is how they are caused.
The most common is exogenous Cushing syndrome and is found in people taking cortisol-like medications such as prednisone. These drugs are used to treat inflammatory disorders such as asthma and rheumatoid arthritis. They also suppress the immune system after an organ transplant. This type of Cushing is temporary and goes away after the patient has finished taking the cortisol-like medications.
Cortisol is sometimes called “the stress hormone” because one of its most important functions is to help the body respond to stress.
Endogenous Cushing syndrome, in which the adrenal glands produce too much cortisol, is uncommon. It usually comes on slowly and can be difficult to diagnose. This type of Cushing is most often caused by hormone-secreting tumors of the adrenal glands or the pituitary, a gland located at the base of the brain. In the adrenal glands, the tumor (usually non-cancerous) produces too much cortisol. In the pituitary, the tumor produces too much ACTH—the hormone that tells the adrenal glands to make cortisol. When the tumors form in the pituitary, the condition is often called Cushing disease.
Most tumors that produce ACTH originate in the pituitary but sometimes non-pituitary tumors, usually in the lungs, can also produce too much ACTH and cause Cushing syndrome.
Three tests are commonly used to diagnose Cushing syndrome. One of the most sensitive tests measures cortisol levels in the saliva between 11:00 p.m. and midnight. A sample of saliva is collected in a small plastic container and sent to the laboratory for analysis. In healthy people, cortisol levels are very low during this period of time. In contrast, people with Cushing syndrome have high levels.
Cortisol levels can also be measured in urine that has been collected over a 24-hour period.
In another screening test, people with suspected Cushing syndrome have their cortisol levels measured the morning after taking a late-night dose of dexamethasone, a laboratory-made steroid. Normally, dexamethasone causes cortisol to drop to a very low level, but in people with Cushing syndrome, this doesn’t happen.
The treatment for Cushing syndrome depends on the cause.
Exogenous Cushing syndrome goes away after patients finish taking the cortisol-like medications they were using to treat another condition. Your doctor will determine when it is appropriate for you to slowly decrease and eventually stop using the medication.
For endogenous Cushing syndrome, the initial approach is almost always surgery to remove the tumor that is causing high cortisol levels. Although surgery is usually successful, some people may also need medications that lower cortisol or radiation therapy to destroy remaining tumor cells. Some people must have both adrenal glands removed to control Cushing syndrome.