What is Cushing's syndrome?

Cushing's syndrome is a rare disorder that develops when the body is exposed to too much of the hormone cortisol. Cushing's syndrome is also known as hypercortisolism.

Normally, cortisol levels increase through a chain reaction of hormones. The brain's hypothalamus produces corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to make adrenocorticotropic hormone (ACTH). Then, ACTH stimulates the adrenal glands to produce cortisol.

Cortisol affects almost every area of the body and is particularly important in regulating blood pressure and metabolism.

But if your body makes too much cortisol-or if you take certain medicines that act like cortisol-you may develop one or more symptoms. Cushing's syndrome may cause weight gain, skin changes, and fatigue and lead to such serious conditions as diabetes, high blood pressure, depression, and osteoporosis. If untreated, Cushing's syndrome can cause death.

What causes Cushing's syndrome?

Cushing's syndrome may be caused by:

• Taking corticosteroid medicine after an organ transplant or for long-term (chronic) conditions such as lupus, asthma, rheumatoid arthritis, or other diseases that cause inflammation. This is the most common cause of Cushing's syndrome.
• Small, noncancerous (benign) tumors on the pituitary gland. This is called Cushing's disease and is the second most common cause of Cushing's syndrome.
• Benign and cancerous tumors on the adrenal glands that make cortisol.
• Benign and cancerous tumors on the lung and less often the pancreas that make ACTH. These organs normally do not make ACTH.

What are the symptoms?

Weight gain and obesity-especially around the waist-are the most common symptoms. Because cortisol affects almost all body systems, many symptoms may develop. They include:

• Muscle weakness.
• Changes in the skin, such as bruising, acne, and dark purple-red stretch marks on the abdomen called striae.
• Changes in mood, such as irritability, anxiety, and depression.
• Extra fat on the back of the neck and upper back.
• Backaches.
• Loss of muscle tone.
• Menstrual irregularity.
• Abnormal hair growth (such as facial hair in women).

The signs and symptoms of Cushing's syndrome generally develop gradually.

Sometimes alcoholism, depression, panic attacks, obesity, or other conditions can cause symptoms similar to Cushing's syndrome. This is known as pseudo-Cushing's syndrome. Symptoms usually stop when these conditions are treated. Antiviral therapies used in the treatment of HIV also may cause pseudo-Cushing's syndrome.

How is Cushing's syndrome diagnosed?

Your doctor will use your medical history, a physical examination, and laboratory tests to diagnose Cushing's syndrome. During the physical examination, he or she will look for signs of the condition. The medical history includes questions about any symptoms you have, what medicines you are taking, and, if you are a woman, whether your menstrual periods are regular.

If your doctor thinks you may have Cushing's syndrome, you will have laboratory tests to check the level of cortisol in your blood and urine. Further testing may be needed to find the cause of high cortisol levels.