How is Cushing’s Syndrome Diagnosed?

The signs are hard to see and may be masked by other health problems. You will need to see your health care provider to find out if CS is a possibility. A diagnosis is based on:

  • Your health history
  • A physical exam
  • Lab tests for cortisol levels

Dexamethasone Suppression Test

Dexamethasone (steroid) pill is given by mouth for this test. Then blood is collected to measure cortisol levels in the body. Normally, the extra steroid would make the body stop making cortisol. In a person with CS, the levels of cortisol will stay very high.

24-Hour Urinary Free Cortisol Test

Urine testing is sometimes used to test cortisol levels. Urine samples are collected for a full period of 24 hours, and tested. To diagnose adrenal problems, more tests would be needed.

Further Tests

Once CS has been diagnosed, imaging and other tests may be used to find the cause. Blood tests and imaging tests can find unwanted tumors. In blood tests, doctors will look for:

  1. Very low levels of corticotropin, which suggests an adrenal tumor. CT scan or MRI usually confirms the diagnosis.
  2. Slightly high levels of corticotropin, which suggests a pituitary tumor. MRI of the brain can often confirm this diagnosis. More tests may be needed if the pituitary tumor is too small to be seen with an MRI.
  3. Very high levels of ACTH suggest an ectopic ACTH. More tests would be needed to confirm this.

Imaging Tests

A CT scan or MRI can often find pituitary or adrenal tumors. These tests show different views of the body in detail. They are painless, accurate and quick.