Question:
Nelson syndrome is most likely seen after:
Nelson syndrome is most likely seen after:
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Loss of cortisol feedback unleashes a pituitary ACTH adenoma.
Updated On: Jun 24, 2026
- Hypophysectomy
- Adrenalectomy
- Thyroidectomy
- Orchidectomy
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The Correct Option is B
Solution and Explanation
Step 1: Nelson syndrome is the rapid enlargement of a pre-existing ACTH-secreting pituitary adenoma that occurs after bilateral adrenalectomy, classically done for Cushing disease.
Step 2: Once both adrenals are removed, cortisol production stops. The normal negative feedback of cortisol on the pituitary is lost, so ACTH secretion surges and the adenoma is no longer held in check and grows.
Step 3: Patients show marked hyperpigmentation from high ACTH and signs of an expanding sellar mass such as headache, visual field defects and cavernous sinus invasion. ACTH levels are very high and these tumours are aggressive. Preoperative pituitary radiotherapy can help prevent it.
Step 4: Hypophysectomy removes the pituitary itself, so no adenoma is left to grow. Thyroidectomy and orchidectomy do not affect the cortisol-ACTH axis. Hence adrenalectomy is the correct trigger.
Step 2: Once both adrenals are removed, cortisol production stops. The normal negative feedback of cortisol on the pituitary is lost, so ACTH secretion surges and the adenoma is no longer held in check and grows.
Step 3: Patients show marked hyperpigmentation from high ACTH and signs of an expanding sellar mass such as headache, visual field defects and cavernous sinus invasion. ACTH levels are very high and these tumours are aggressive. Preoperative pituitary radiotherapy can help prevent it.
Step 4: Hypophysectomy removes the pituitary itself, so no adenoma is left to grow. Thyroidectomy and orchidectomy do not affect the cortisol-ACTH axis. Hence adrenalectomy is the correct trigger.
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