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Primary vs Secondary Adrenal Insufficiency — SCE Medical Oncology MCQ

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HardMelanoma & SkinPrimary vs Secondary Adrenal InsufficiencySCE Medical Oncology

A 55-year-old man with metastatic melanoma on immunotherapy develops new adrenal insufficiency (cortisol <50 nmol/L). His ACTH is elevated (>100 pg/mL). What does this pattern indicate?

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Correct answer: A — Primary adrenal insufficiency (adrenalitis) — the elevated ACTH confirms the adrenal gland is the target of immune destruction, not the pituitary

ICI-induced adrenal insufficiency can be primary (adrenalitis: low cortisol, HIGH ACTH) or secondary (hypophysitis: low cortisol, LOW ACTH). The ACTH level distinguishes: primary = elevated ACTH (pituitary attempting to stimulate failing adrenals); secondary = low ACTH (pituitary itself is damaged). Primary adrenalitis requires both glucocorticoid AND mineralocorticoid replacement (fludrocortisone). Secondary requires glucocorticoid only (ACTH deficiency does not significantly affect aldosterone as it is mainly renin-RAAS regulated).

Reference: ESMO 2024 irAE Management; ASCO Endocrine irAE