Complete remission of Nelson's syndrome after 1-year treatment with cabergoline

In this case report we demonstrated that treatment with the long-acting D2 receptor agonist cabergoline for 1 year induced normalization of plasma ACTH levels and disappearance of the pituitary tumor in a patient with Nelson's syndrome. A young man underwent bilateral adrenalectomy and subsequent pituitary irradiation for Cushing's disease after unsuccessful neurosurgical treatment. Thereafter, he was given cortisone acetate replacement at the dose of 62.5 mg a day. Fifteen months after pituitary irradiation, he developed Nelson's syndrome, having skin hyperpigmentation, high plasma ACTH levels (376 ng/l) and a pituitary microadenoma (5 mm) documented at magnetic resonance imaging (MRI) of the pituitary region. After 6 months of cabergoline treatment, given at the dose of 1 mg a week, plasma ACTH levels were significantly decreased (from 376 to 113 ng/l) but they were not normalized. Cabergoline dose was then increased up to 2 mg a week. Six months later plasma ACTH levels were normalized (22 ng/l) and MRI demonstrated the disappearance of the pituitary adenoma. In order to investigate on the direct effect played by cabergoline treatment on the remission of Nelson's syndrome, the treatment was withdrawn. Plasma ACTH levels significantly increased (119 ng/l) after 3 months of treatment withdrawal. At the last follow-up, during cabergoline treatment at the dose of 2 mg/week plasma ACTH levels were normalized (40.4 ng/l). This case demonstrated that cabergoline treatment is able to induce the remission of Nelson's syndrome and may be a valid therapeutic alternative in this syndrome.