This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pediatrics
Nelson syndrome is seen in: 
Select and explain. 
A. Adrenalectomy, B. Hypopitutarism, C. Deficiency of beta cells, D. Deficiency of growth hormone
A: Adrenalectomy
Answer: A: Adrenalectomy 
Explanation: a. Adrenalectomy(Ref: Nelson's 20/e p 2714-2723, Ghai 8/e p 526-527)Adrenalectomy, in a case of pituitary adenoma, may lead to increased ACTH secretion by an unresected pituitary adenoma, evidenced mainly by marked hyperpigmentation; this condition is termed Nelson syndrome.