Diagnosis

Taking glucocorticoid medications is the most common cause of Cushing syndrome. Your doctor can review all your medications — pills, injections, creams and inhalers — to determine if you're taking medications that can cause the disorder. If you are, you probably won't need other tests.

Cushing syndrome from endogenous cortisol production can be difficult to diagnose because other conditions have similar signs and symptoms. Diagnosing Cushing syndrome can be a long and extensive process. You'll likely need to see a doctor who specializes in hormonal disorders (endocrinologist).

Your doctor will conduct a physical exam and look for indications of Cushing syndrome, such as rounding of the face, a pad of fatty tissue between the shoulders and neck, and thin skin with bruises and stretch marks.

If you haven't been using a corticosteroid medication, these diagnostic tests may help pinpoint the cause:

• Urine and blood tests. These tests measure hormone levels and show whether your body is producing excessive cortisol. For the urine test, you may be asked to collect your urine over a 24-hour period. Urine and blood samples will be sent to a laboratory to be analyzed.

  Your doctor might also recommend other specialized tests that involve measuring cortisol levels before and after using hormone medications to stimulate or suppress cortisol.

• Saliva test. Cortisol levels normally rise and fall throughout the day. In people without Cushing syndrome, levels of cortisol drop significantly in the evening. By analyzing cortisol levels from a small sample of saliva collected late at night, doctors can see if cortisol levels are too high.
• Imaging tests. CT or MRI scans can provide images of your pituitary and adrenal glands to detect abnormalities, such as tumors.

• Petrosal sinus sampling. This test can help determine whether the cause of Cushing syndrome is rooted in the pituitary or somewhere else. For the test, blood samples are taken from the veins that drain the pituitary gland (petrosal sinuses).

  A thin tube is inserted into your upper thigh or groin area while you're sedated and is threaded to the petrosal sinuses. Levels of ACTH are measured from the petrosal sinuses and from a blood sample taken from the forearm.

  If the ACTH level is higher in the sinus sample, the problem stems from the pituitary. If the ACTH levels are similar between the sinuses and forearm, the root of the problem lies outside of the pituitary gland.

These tests help your doctor diagnose Cushing syndrome, and they may help rule out other medical conditions, such as polycystic ovary syndrome — a hormone disorder in women with enlarged ovaries. Depression, eating disorders and alcoholism also can partially mimic Cushing syndrome.