We report the results of long-term (6-year) treatment of Nelson's syndrome with 
the long-acting dopamine agonist, cabergoline, in a 55-year-old woman. The 
disease presented 26 years after bilateral adrenalectomy and radiation treatment 
for Cushing's disease, followed by glucocorticoid and mineralocorticoid 
replacement therapy. Signs of Nelson's syndrome included skin and mucosal 
hyperpigmentation accompanied by elevated plasma levels of adrenocorticotropic 
hormone (ACTH) (984 pmol/l; normal, 2.0-11.5 pmol/l). Magnetic resonance imaging 
of the pituitary demonstrated sellar enlargement with a 15 mm macroadenoma. The 
patient was initially treated with bromocriptine (10 mg/d) which had no effect 
on either ACTH level or tumor mass. Because of visual loss, transsphenoidal 
surgery was performed, with partial excision of the adenoma and chiasmal 
decompression, followed by radiosurgery. However, ACTH levels improved only 
temporarily, and then increased to previous levels. Therefore, cabergoline 
treatment (1.5 mg/week) was initiated. ACTH levels decreased dramatically from 
1050 to 132 pmol/l, accompanied by clinical improvement. Repeated imaging 
studies demonstrated a stable residual pituitary tumor. This case demonstrates 
that long-term cabergoline treatment may be efficient in patients with Nelson's 
syndrome.