Nelson Syndrome

Nelson syndrome is progressive growth of an ACTH secreting pituitary adenoma after bilateral adrenalectomy for Cushing disease.

• Develops in 15 to 30% of patients after adrenalectomy (lower with prior pituitary radiotherapy).
• Loss of cortisol negative feedback leads to tumour expansion and very high ACTH.
• Tumours are often invasive macroadenomas.

• Progressive hyperpigmentation of skin and mucous membranes, scars.
• Headache, visual field defects (bitemporal hemianopia), cranial nerve palsies, hypopituitarism.
• Features of mass effect, rarely apoplexy.

• Very high plasma ACTH (often over 500 pg/mL) with adequate glucocorticoid replacement.
• Pituitary MRI with gadolinium.
• Visual fields, pituitary function tests.
• Surveillance MRI after adrenalectomy (every 3 to 6 months initially, then yearly).

• Transsphenoidal surgery for resectable tumour (first line).
• Radiotherapy (fractionated or stereotactic radiosurgery) for residual or invasive tumour.
• Medical: cabergoline 0.5 to 3.5 mg weekly, pasireotide 600 to 900 micrograms SC twice daily, temozolomide 150 to 200 mg/m2 for 5 days every 28 days for aggressive tumours.
• Adequate glucocorticoid replacement (hydrocortisone 15 to 25 mg daily) and fludrocortisone; avoid under replacement.
• Prevention: pituitary radiotherapy at adrenalectomy in selected cases; careful follow up.