Clinical and biochemical stabilization of Nelson's syndrome with long-term low-dose cabergoline treatment.

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.