Nelson syndrome

Nelson syndrome is a rare endocrine disorder that develops in patients who have previously undergone bilateral adrenalectomy (surgical removal of both adrenal glands) as a treatment for Cushing disease. After adrenalectomy, the loss of cortisol feedback allows a pre-existing corticotroph pituitary adenoma (ACTH-secreting tumor) to grow aggressively. The condition is characterized by markedly elevated adrenocorticotropic hormone (ACTH) levels, progressive enlargement of the pituitary tumor, and hyperpigmentation of the skin and mucous membranes due to the melanocyte-stimulating effects of high ACTH and its precursor pro-opiomelanocortin (POMC). The expanding pituitary mass can compress surrounding structures, leading to visual field defects (particularly bitemporal hemianopia), headaches, and hypopituitarism affecting multiple hormonal axes. Nelson syndrome typically develops months to years after bilateral adrenalectomy, with reported incidence rates varying widely (approximately 8–38% of patients who undergo the procedure for Cushing disease). The condition primarily affects the endocrine and neurological systems. Patients may present with progressive darkening of the skin, visual disturbances, cranial nerve palsies, and symptoms related to deficiencies in thyroid, gonadal, and growth hormones if the tumor damages normal pituitary tissue. In some cases, the tumor may behave aggressively with local invasion into the cavernous sinuses or other adjacent structures. Treatment of Nelson syndrome is multimodal. Pituitary surgery (typically transsphenoidal resection) is considered the first-line treatment to debulk or remove the tumor. Radiation therapy, including conventional radiotherapy and stereotactic radiosurgery (such as Gamma Knife), may be used as adjunctive treatment or when surgery is not feasible or incomplete. Medical therapies, including somatostatin analogs (e.g., pasireotide) and temozolomide for aggressive tumors, have been explored with variable success. Lifelong glucocorticoid and mineralocorticoid replacement therapy is necessary following bilateral adrenalectomy. Regular monitoring with MRI imaging and ACTH levels is essential for early detection and management of tumor progression.

Common questions about Nelson syndrome