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Primary Adrenal ICI Fludrocortisone — SCE Medical Oncology MCQ

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ModerateImmunotherapy & Targeted TherapyPrimary Adrenal ICI FludrocortisoneSCE Medical Oncology

A 58-year-old man on ICI for NSCLC develops immune-related adrenal insufficiency. His morning cortisol is 45 nmol/L. ACTH is elevated at 350 pg/mL. He is started on hydrocortisone. Does he also need mineralocorticoid replacement?

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Correct answer: E — Yes — PRIMARY adrenal insufficiency (high ACTH = adrenal target) requires BOTH glucocorticoid (hydrocortisone) AND mineralocorticoid (fludrocortisone) replacement, unlike secondary (hypophysitis: low ACTH) which needs glucocorticoid only

Primary adrenal insufficiency (adrenalitis): both cortisol AND aldosterone production fail. ACTH is elevated (attempting to stimulate failing adrenals). Treatment: hydrocortisone (20-30mg daily in divided doses) + fludrocortisone (50-200mcg daily). Secondary (hypophysitis): ACTH is low/absent; aldosterone is preserved (renin-RAAS regulated) → glucocorticoid only.

Reference: ESMO 2024 irAE; Endocrine Society Adrenal Insufficiency; BNF