Nelson syndrome

Nelson syndrome is a condition that can develop after surgery to remove part of the pituitary gland to treat Cushing’s disease, which causes excess cortisol. When the tumor that produced the high cortisol is removed, the remaining pituitary cells—particularly those that produce a hormone called ACTH—may become overactive or grow larger. This leads to high levels of ACTH in the blood, causing skin darkening (hyperpigmentation) and, sometimes, the growth of tumors in the pituitary area that may press on nearby structures. Regular monitoring is important to detect and manage these changes early.