Cushing’s syndrome can be caused by medication or by a tumor. Sometimes, there is a tumor of the adrenal gland that makes too much cortisol. It may also be caused by a tumor in the pituitary gland (a small gland under the brain that produces hormones that in turn regulate the body’s other hormone glands).
Some pituitary tumors produce a hormone called adrenocorticotropic hormone (ACTH ), which stimulates the adrenal glands and causes them to make too much cortisol. This is termed Cushing’s disease. ACTH -producing tumors can also originate elsewhere in the body and these are referred to as ectopic tumors.
It is important to note that pituitary tumors are almost never cancerous.