People who have both their adrenal glands removed as treatment for Cushing disease that did not resolve with surgery and/or radiation to the pituitary may develop Nelson syndrome.

In this disorder, the pituitary tumor that caused the Cushing disease continues to grow, producing large amounts of ACTH and leading to darkening of the skin. The enlarging pituitary tumor may compress nearby structures in the brain, causing headaches and defects in vision.

Some experts believe that this compression may be prevented, at least in some people, by radiation therapy to the pituitary gland. If necessary, Nelson syndrome can be treated with radiation therapy or surgical removal of the pituitary gland.