[Nelson's Syndrome].

Nelson's syndrome is a rare condition defined by enlargement of a pituitary adenoma following bilateral adrenalectomy for treatment of Cushing disease. Nelson's syndrome occurs at an incidence of 8-38% and is more frequent in younger people. This syndrome is characterized by skin hyperpigmentation and very high circulating levels of adrenocorticotrophic hormone. The pathophysiology of the disease is still not fully understood, and it is unknown what factors drive corticotroph cells in these patients. Presently, the syndrome is diagnosed at earlier stages and therefore its clinical manifestation is less typical than in the past. However, we can still find cases of full-blown Nelson's syndrome, resulting from massive tumor growth and dramatically increased production of adrenocorticotrophic hormone. Treatment of this syndrome largely consists of surgery and/or radiotherapy because of the limited effectiveness of pharmacotherapy. Although no guidelines have been published, it is reasonable to perform pituitary imaging and to assess adrenocorticotrophic hormone in all patients, particularly during the first years after bilateral adrenalectomy. The purpose of this paper is to review the current views on the etiopathogenesis, clinical presentation, diagnosis and treatment of Nelson's syndrome.