This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Parathyroid and adrenal glands, Subject name: Surgery
After bilateral adrenalectomy, patient developed gradual loss of vision, with hyperpigmentation of skin, and headache. Likely cause is: 
Select and explain. 
A. Addison's disease, B. Nelson's syndrome, C. Cushing's disease, D. Hypopituitarism
B: Nelson's syndrome
Answer: B: Nelson's syndrome 
Explanation: NELSON'S SYNDROME Adrenalectomy in the setting of residual coicotroph adenoma tissue predisposes to the development of Nelson's syndrome. Characterized by rapid pituitary tumor enlargement and increased pigmentation secondary to high ACTH levels. Radiation therapy may be indicated to prevent the development of Nelson's syndrome after adrenalectomy. Primary adrenal Cushing's syndrome - Adrenalectomy - Loss of negative feedback to pituitary - Development of pituitary adenoma - Nelson's syndrome.