Pituitary corticotroph hyperplasia preceding adenoma in a patient with Nelson's syndrome

We report the case of a 42-year-old woman with Cushing's disease and Nelson's syndrome. When she was 17 years old, transsphenoidal surgery was performed. A detailed morphologic study demonstrated nodular hyperplasia of corticotroph cells but no adenoma. Following a long-lasting remission (14 years), Cushing's disease recurred. After an unsuccessful second transsphenoidal surgery, Cushing's disease persisted and both adrenals were removed (at the age of 34). Subsequently the patient developed Nelson's syndrome. The pituitary tumor proved to be a corticotroph adenoma; it was removed by the transsphenoidal approach (at the age of 42). Although in most patients Cushing's disease is due to an ACTH-secreting pituitary corticotroph adenoma which precedes the manifestation of Nelson's syndrome, our case indicates not only that corticotroph hyperplasia may cause Cushing's disease but that it may exist before the development of Nelson's syndrome after the removal of both adrenals. Our study supports the view that protracted stimulation of corticotrophs resulting from the elimination of the negative inhibitory feedback effect by corticosteroids plays a role in adenoma initiation.