The corticotropin-releasing hormone (CRH) stimulation test helps find out if a pituitary tumor may be causing Cushing's syndrome. It is sometimes done with an inferior petrosal sinus sampling (IPSS) test.
In these tests, a small tube called a catheter is used. A health professional uses it to collect samples from blood vessels coming from the pituitary gland near the brain and also from a vein in your arm. First you will get a shot of CRH. Then samples of your blood near your pituitary gland and from your arm are taken.