Cushing syndrome happens when you have too much cortisol in your body. When the disorder starts with the pituitary gland, the condition is called Cushing disease. The gland makes too much adrenocorticotropic hormone (ACTH). That causes the adrenal glands to make too many corticosteroids (mainly cortisol).
Another main cause is taking steroid medicines like prednisone for a long time. These are sometimes used to treat chronic diseases such as asthma or rheumatoid arthritis. Other causes include:
- Some types of lung cancer.
- Noncancerous (benign) or cancerous tumors on the adrenal glands.
- An inherited endocrine disorder.