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Cushing's Syndrome Diagnosis

Your doctor may start by asking you questions and doing a physical exam. If the cause is a medicine you are taking, no tests are needed. If your doctor thinks that you have Cushing's syndrome or disease, but no medicines are causing it, you may need to have some blood and urine tests.

Your doctor may ask you to collect your urine for 24 hours. Be sure to do what the doctor tells you to do for this test. Your doctor may have you take a medicine called dexamethasone before your blood or urine is collected. This tests your body's response to steroids.

Cushing's Syndrome Diagnosis - Tests to confirm high cortisol level:

cortisol, urine
dexamethasone suppression test
serial serum cortisol levels do not show diurnal variations

Cushing's Syndrome Diagnosis - Tests to determine the cause:

ACTH
cranial MRI or cranial CT scan may show pituitary tumor
abdominal CT may show adrenal mass

More detailed information about Cushing's Syndrome Diagnosis

Most people who appear to have some of the classic physical features of Cushing's Syndrome (cushingoid appearance) do not actually have the disease. After iatrogenic Cushing's is excluded, other causes of this appearance cn be polycystic ovary syndrome (androgen excess from the ovaries), ovarian tumors, congenital adrenal hyperplasia, ordinary obesity, excessive alcohol consumption, or just a family tendency to have a round face and abdomen with high blood pressure and high blood sugar.

Because Cushing's Syndrome is a rare but serious disorder, it is very important to carefully exclude (rule out) other disorders and then separate the different types, leading eventually to a specific cause that can be treated. This process of testing and excluding usually takes days to weeks and requires a lot of patience and cooperation by the person being tested.

After the initial history, physical exam and routine blood tests, the first step is to prove cortisol excess with specific blood and 24 hour urine tests for cortisol. Inappropriate cortisol production will then be evaluated by doing a dexamethasone suppression test. Dexamethasone (steroid) pills are given by mouth, then blood and urine are collected for cortisol and other adrenal hormones. A screening test might be done initially with an overnight test, but if it is abnormal, usually a 4 day test divided into low and high dose dexamethasone is needed. To separate ACTH dependent from independent types, a blood test for ACTH in the morning is done. Blood and urine tests for adrenal androgens are useful. Testing with other drugs, such as metyrapone and CRH (corticotropin releasing hormone) may also be needed.

Once all of the blood and urine results are analyzed, they will establish whether some type of Cushing's Syndrome is present, and should indicate whether the disease is ACTH dependent (pituitary or ectopic) or independent (an adrenal tumor). Localizing techniques such as CT or MRI are then used to find the tumor. Often a pituitary tumor is tiny and hard to find, so a special test of the release of ACTH from both sides of the pituitary (petrosal sinus sampling) might be needed. Small tumors producing ectopic ACTH are also sometimes difficult to localize and require repeated scans and x-rays.

Cushing's syndrome picture and information

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