What is Cushing syndrome?

Illustration of a semicircular meter with sections going from green to yellow to orange to red, with the word cortisol above it, low at the bottom left corner and high at the bottom right corner, and a silver arrow in the center pointing toward the high end.

High levels of cortisol in your body can result in Cushing syndrome. Left untreated, Cushing syndrome can cause distressing symptoms and lead to serious health complications. Fortunately, tests can help determine the cause of high cortisol levels, which can guide treatment

Cushing syndrome, also known as hypercortisolism, occurs when you have higher-than-normal levels of cortisol in your body for a significant duration of time. Cortisol is a hormone made by your adrenal glands, two small glands located next to the kidneys. You can have high levels of cortisol if your adrenal glands overproduce it, or if you take cortisol-like medications (glucocorticoids) at high doses for a long time to treat another condition. The high cortisol levels can cause various symptoms and possible health complications.

In normal amounts, cortisol helps your body maintain blood pressure and blood sugar level, reduce inflammation, and regulate salt balance, among other functions. Cortisol is also directly connected to the body's stress response. Your body releases cortisol to help you deal with stressful situations.

Cushing syndrome due to your own body making too much cortisol (rather than taking too much) affects about three times as many women as men, and is most common in people ages 20 to 50. Cushing syndrome is considered rare, but the actual number of people who have it is unknown since some go undiagnosed.

"In Cushing syndrome, there are clinical signs that indicate your body has too much cortisol," explained Dr. Lisa Nachtigall, clinical director of the Neuroendocrine & Pituitary Tumor Clinical Center at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School. "Once high cortisol levels are established, the next step is to figure out why that is happening."

What can cause Cushing syndrome?

The most common cause of Cushing syndrome is long-term use of glucocorticoids. Glucocorticoids are steroids used to treat a variety of conditions including asthma, cancer, inflammatory bowel disease, lupus, joint pain, and rheumatoid arthritis. They are also used to prevent transplant rejection. Examples of glucocorticoids are cortisone, prednisone, dexamethasone, and prednisolone.

Less often, Cushing syndrome occurs when the body makes too much cortisol. This is usually caused by a tumor (typically noncancerous) in the pituitary gland. Located at the base of your brain, the pituitary gland produces a hormone called adrenocorticotropic hormone (ACTH) that normally instructs the adrenal glands to make cortisol. A tumor can spur the pituitary gland to produce too much ACTH, which in turn causes the adrenal glands to produce too much cortisol. This form of Cushing syndrome is called Cushing disease.

In other cases, tumors in other organs can produce ACTH and lead to Cushing syndrome. Finally, the adrenal glands themselves can develop tumors that overproduce cortisol and can lead to Cushing syndrome.

Symptoms of Cushing syndrome

Symptoms of Cushing syndrome include:

weight gain, especially around the abdomen
rounded face, sometimes called Cushing syndrome moon face
a fat pad on the back of the neck
purple or red stretch marks, usually around the abdomen, chest, and underarms
easy bruising
high blood pressure (hypertension)
high blood sugar and diabetes
muscle weakness
thinning bones (osteoporosis)
depression and problems with thinking
too much facial hair in women (hirsutism)
erectile dysfunction (ED) in men.

Left untreated, Cushing syndrome increases the risk of hypertension, diabetes, skeletal fractures, blood clots, heart attack, stroke, and increased risk of infections.

Diagnosing Cushing syndrome

Because symptoms of Cushing syndrome can mimic many other conditions, diagnosis can be challenging.

Dr. Nachtigall points out that many people have symptoms of Cushing syndrome for years before they are diagnosed. "Unfortunately, Cushing syndrome isn't easy to diagnose," she says, "which can be very frustrating and overwhelming for patients."

Diagnosing Cushing syndrome is usually straightforward in people who are taking glucocorticoids. For others, tests used for diagnosis include:

Dexamethasone suppression test (DST). You take a low dose of the glucocorticoid dexamethasone at night and have your blood drawn in the morning. Cortisol levels normally drop after taking dexamethasone, so high levels are a sign of Cushing syndrome.
24-hour urinary free-cortisol test. You collect your urine over 24 hours and have it analyzed in a lab. According to Dr. Nachtigall, this test is better than DST but is less sensitive early in the course of Cushing syndrome.
Salivary test. This measures the level of cortisol in your saliva late at night, when normal cortisol production should decrease. You collect your saliva at home at your usual bedtime and have it sent to a lab for testing.

Once your doctor diagnoses Cushing syndrome, the next step it to determine why it has happened. Knowing the cause of high cortisol levels guides the treatment.

If you take glucocorticoid medication, that's likely the cause of your Cushing syndrome. If Cushing syndrome is caused by the body's overproduction of cortisol, and after the high levels of cortisol have been definitively confirmed, the following tests can help pinpoint the specific reason:

blood tests to measure levels of the hormone ACTH in your body (this indicates whether a tumor is in your pituitary gland, adrenal glands, or elsewhere in your body)
imaging studies such as a CT scan or MRI, which can identify tumors on the pituitary or adrenal glands.

Cushing syndrome treatment

Without treatment, Cushing syndrome can be life-threatening.

If Cushing syndrome is caused by glucocorticoids you are taking to treat another medical condition, you may be able to work with your doctor to gradually and carefully reduce your dose.

If a tumor is causing the disorder, you may need surgery to remove it. Medical therapies such as cortisol-blocking drugs may also be needed.

Dr. Nachtigall coauthored a research study on Cushing syndrome, which found that about 10% of people with Cushing syndrome develop an autoimmune disease after they are surgically treated and in remission. Some people have problems with memory and mood afterward as well. These problems may require additional medical therapy, says Dr. Nachtigall, but most symptoms improve after treatment.

Cushing syndrome may come back, even years later. Being aware of the symptoms of Cushing syndrome, and getting treated early, can help prevent long-term effects.

Lifestyle changes to help manage Cushing syndrome

If you have Cushing syndrome, good lifestyle habits are key to avoiding complications. Having a healthy diet and getting regular exercise are essential, says Dr. Nachtigall.

Blood pressure can be high in people with Cushing syndrome; checking blood pressure and taking blood pressure-lowering medication if required can help. Cushing syndrome also increases the risk of osteoporosis. Maintaining bone strength through exercise and a healthy diet with adequate calcium and vitamin D intake, and making efforts to prevent falls (which can lead to fractures) are also important.