Rare condition resulting from removal of both adrenal glands due to Cushing syndrome. Several months to years after adrenal gland removal, patients experience abnormally high levels of cortisol, which may cause secretions that stimulate corticotroph tumor growth. Characterized by enlarged pituitary tumor, progressive hyperpigmentation, headache, increased plasma adrenocorticotropic hormone levels, and visual field defect in association with a history of Cushing syndrome. Other manifestations are tumor-related symptoms including headaches and visual field defects.

Diagnosis of Nelson syndrome at an earlier stage allows for treatment by radiation therapy, which can significantly reduce tumor growth. Other treatments include transsphenoidal surgery, postoperation radiotherapy, and administration of an alkylating agent. Early detection and intervention contributes to a more positive prognosis. Prognosis, however, is not good for enlarged, invasive macroadenomas where diagnosis and treatment were delayed.