How is Cushing's syndrome diagnosed?
To diagnose Cushing's syndrome, doctors review the patient's medical records and do a physical exam. If these suggest Cushing's syndrome, more tests are done. A definite diagnosis involves seeing if there is too much cortisol in the body, and
discovering the cause of extra cortisol. A urine test measures how much cortisol is being produced. If the level indicates Cushing's syndrome, the doctor will order other tests to discover the cause. These may include biochemistry tests. The dexamethasone suppression test involves taking a man-made cortisol by mouth for several days during which time cortisol levels in the blood and urine are measured.
The CRH stimulation test involves receiving an injection of the corticotropin-releasing hormone (CRH) followed by a blood test to see if there is a rise in the levels of ACTH and cortisol. Other procedures may include computerized tomography (CT) and magnetic resonance imaging (MRI) scans of the pituitary and adrenal glands, chest, and abdomen; ultrasound imaging of the adrenal glands; chest x-rays; and perhaps a radioisotope procedure called an iodocholesterol scan. Samples of the blood leaving the pituitary gland are tested to see if the pituitary is causing the high level of ACTH.