Addison's Disease — Adrenal Insufficiency
A patient presents with hyperpigmented skin creases, salt cravings, and fatigue that worsens with stress. The skin color isn't a tan — it's a warning sign the adrenals are failing.
Core Concept
Addison's disease is primary adrenal insufficiency — the adrenal cortex is destroyed (most commonly by autoimmune attack), so it cannot produce adequate cortisol, aldosterone, or adrenal androgens. Without cortisol, the body loses its ability to mount a stress response, maintain blood glucose, and suppress inflammation. Without aldosterone, sodium is wasted in the urine and potassium is retained, causing hyponatremia, hyperkalemia, and hypotension. The hallmark bronze hyperpigmentation occurs because the pituitary detects low cortisol and ramps up ACTH production. ACTH shares a precursor molecule (POMC) with melanocyte-stimulating hormone, so excess ACTH drives melanin production — darkening skin folds, palmar creases, buccal mucosa, and scars. Key labs: low cortisol, low sodium, high potassium, high ACTH, possible hypoglycemia. The ACTH stimulation test confirms diagnosis — cortisol fails to rise after synthetic ACTH injection. Lifetime glucocorticoid replacement (hydrocortisone) is the cornerstone, often paired with fludrocortisone for mineralocorticoid replacement. The client must understand stress dosing: doubling or tripling the glucocorticoid dose during illness, injury, or surgery to prevent adrenal crisis.
Watch Out For
Don't confuse Addison's (low cortisol, hyperpigmentation, hypotension, hyperkalemia) with Cushing's (excess cortisol, moon face, hypertension, hypokalemia) — they are clinical mirrors. Students mix up the potassium direction: Addison's = high K+, Cushing's = low K+. ACTH is high in Addison's (primary) because the pituitary is screaming at failing adrenals; in secondary adrenal insufficiency, ACTH is low because the pituitary itself is the problem.
Clinical Pearl
Think 'Addison's Adds potassium and ACTH, but subtracts sodium, cortisol, and blood pressure.' The 3 H's: Hyperpigmented, Hypotensive, Hyperkalemic.
Test Your Knowledge
3 quick questions — see how well you understood Addison's Disease — Adrenal Insufficiency