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Addison's Disease — RACP Adult Medicine MCQ

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EasyEndocrinology & DiabetesAddison's DiseaseRACP Adult Medicine

A 55-year-old man presents with progressive fatigue, orthostatic hypotension, skin hyperpigmentation, and hyponatraemia (Na 128 mmol/L). His serum cortisol at 9 AM is 80 nmol/L. Short Synacthen test shows cortisol of 120 nmol/L at 30 minutes (inadequate response). ACTH is markedly elevated at 450 pg/mL. What is the most appropriate initial treatment?

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Correct answer: C — Hydrocortisone 20 mg mane, 10 mg afternoon PLUS fludrocortisone 100 mcg daily

Primary adrenal insufficiency (Addison's disease – elevated ACTH with low cortisol) requires both glucocorticoid (hydrocortisone 15–25 mg/day in divided doses, usually 20 mg on waking, 10 mg early afternoon) AND mineralocorticoid (fludrocortisone 50–200 mcg daily) replacement. The pigmentation is due to elevated ACTH/MSH. Patients must be educated about sick-day rules and carry a steroid emergency card and injectable hydrocortisone.

Reference: eTG – 2025 – Endocrinology; Endocrine Society – 2016 – Adrenal Insufficiency Guidelines