Cushing’s Syndrome Diagnosis
Exams and Tests for Cushing’s Syndrome
Often times, several tests are needed to confirm a Cushing's syndrome diagnosis—and your doctor will want to rule out other conditions.
Diagnosing Cushing's syndrome starts with a doctor's visit—your doctor will do a physical exam and ask about your personal medical history. He or she will ask you if you are currently taking corticosteroids or have used them in the past because taking these medications long term can lead to Cushing's syndrome.
Your doctor will also ask you about your family medical history since it's possible to inherit conditions (eg, multiple endocrine neoplasia type 1) that cause tumors to develop on one or more of your endocrine glands.
During your physical, your doctor may notice obvious signs of Cushing's syndrome, such as weight gain around the stomach and thin arms and legs, but to confirm a Cushing's syndrome diagnosis and help identify the cause, your doctor may order special tests.
Tests for Cushing's Syndrome
- Blood and urine tests: These tests help your doctor identify the amount of hormones, such as cortisol and adrenocorticotropic hormone (ACTH), in your body. For example, if your body is producing too much cortisol, a hormone released by your adrenal glands, it will show up in your blood and urine tests. A common urine test is the 24-hour urine test for cortisol.
Another common test is the dexamethasone-suppression test. Dexamethasone is a corticosteroid—similar to a natural hormone produced by your adrenal glands. The body's normal response to taking dexamethasone is to stop making cortisol temporarily because the brain recognizes that dexamethasone is present and that it doesn't need to send the ACTH signal to make the body's own cortisol. However, people with Cushing's syndrome continue to make cortisol even when dexamethasone is taken.
Your doctor may also recommend other more specialized blood and urine tests to help determine if you have Cushing's syndrome and to help figure out the underlying source of excessive hormone production.
- Saliva test: It's normal for cortisol levels to change throughout the day—levels are highest in the morning and very low or undetectable around midnight. However, people with Cushing's syndrome show less variability in their cortisol levels and have higher levels than normal at night. Your doctor can check your cortisol levels using a small late-night salivary sample.
- Imaging tests: Specific imaging tests, such as computerized tomography (CT) scans or magnetic resonance imaging (MRI) scans can help your doctor spot any abnormalities in your pituitary gland and/or adrenal glands.
Some of the imaging tests your doctor may recommend are:
- abdominal CT to check for an adrenal gland tumor or another type of tumor in the abdomen
- pituitary MRI to look for a pituitary gland tumor
- dual x-ray absorptiometry (DXA) to measure bone mineral density; often times, people with Cushing's syndrome have low bone mass.
The exams and tests listed in this article will help your doctor diagnose Cushing's syndrome—as well as identify its cause. The sooner you're diagnosed with Cushing's syndrome, the sooner you can begin treatment for Cushing's syndrome.