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Checkpoint inhibitor-induced hypophysitis — SCE Endocrinology MCQ

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HardAdrenalCheckpoint inhibitor-induced hypophysitisSCE Endocrinology

A man receiving immune-checkpoint inhibition develops headache, nausea and fatigue. Sodium is 122 mmol/L, 09:00 cortisol 48 nmol/L with low ACTH, and free T4 is low with an inappropriately normal TSH. What is the unifying diagnosis?

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Correct answer: B — Checkpoint-inhibitor-induced hypophysitis

Low cortisol with low ACTH and low free T4 with non-raised TSH identify combined central adrenal and thyroid failure. In the context of checkpoint inhibition and headache, hypophysitis is the unifying diagnosis. Glucocorticoid replacement must precede levothyroxine when both axes are deficient.

Reference: NICE NG243 recommendations for adrenal insufficiency (Published 28 August 2024): https://www.nice.org.uk/guidance/ng243/chapter/Recommendations; Society for Endocrinology emergency guidance for pituitary apoplexy (Current Society emergency guidance, accessed 30 July 2026): https://www.endocrinology.org/media/1132/2011-04-14_pituitary-apoplexy.pdf