Cushing vs Addison
Both are the adrenal cortex gone wrong on cortisol — Cushing is too much, Addison is too little. One puffs the patient up and props them up; the other wastes them away and drops them out. Nail the direction and every lab, every finding, every drug falls into place. And remember the one exception to "everything is opposite": the skin story runs its own way.
🧠 Memory Tricks
Cushing
- Cushing = "Cushion" → puffy, padded, cushioned body (moon face, buffalo hump, truncal fat). Everything is HIGH (sugar, salt, BP) except potassium is LOW.
Addison
- Addison = "Add-a-son a steroid" → the patient is missing cortisol, so you add it back for life. Everything is LOW (BP, glucose, sodium) except potassium is HIGH.
- The lab that flips: potassium. Cortisol/aldosterone dump K⁺, so excess (Cushing) → low K⁺, deficiency (Addison) → high K⁺. If you only memorize one lab, memorize potassium.
- Skin sound-alike: Addison = A tan (bronze); Cushing = Cracked, thin, bruised skin with purple striae.
🟢 Step 1 — What's Normal (Shared by all)
Picture it: The adrenal cortex is the body's "stress supply depot." Cortisol is the manager who turns UP sugar, salt/water, and blood pressure so you can survive a threat; aldosterone is the salt-and-water clerk; androgens are a side inventory. Turn the depot's output up too far or shut it down and the whole warehouse spills or empties.
The player(s): The adrenal cortex (outer shell of each adrenal gland, sitting on top of each kidney), driven by pituitary ACTH. It makes three hormone families: cortisol (the stress steroid), aldosterone (the salt-keeping mineralocorticoid), and adrenal androgens (sex-steroid precursors).
Its normal job(s):
- Cortisol raises blood glucose — it frees sugar for fuel under stress. (This is what Cushing floods; Addison drains it.)
- Cortisol is anti-inflammatory and tempers immunity — it damps down the inflammatory/immune response. (This is what Cushing over-suppresses → infection risk; Addison loses.)
- Cortisol supports vascular tone / the stress "fight" response — it keeps blood pressure up under stress and lets catecholamines work. (Cushing props BP up → HTN; Addison can't hold it → hypotension/shock.)
- Aldosterone retains Na⁺ and water and excretes K⁺ — it holds salt and water (raising BP) and pushes potassium out in the urine. (Cushing's cortisol excess spills over onto this → high Na⁺, low K⁺; Addison loses aldosterone → low Na⁺, high K⁺.)
- Androgens add secondary sex characteristics — a minor contributor to hair/libido. (Cushing excess → hirsutism; Addison deficiency → less body hair.)
How it works (the sequence): The pituitary releases ACTH → ACTH tells the adrenal cortex to make cortisol → rising cortisol feeds back to shut ACTH off (negative feedback). Aldosterone runs on its own loop (renin-angiotensin + potassium level). Cortisol normally peaks in the morning and troughs at night.
Normal numbers: glucose 70–110 mg/dL; sodium 135–145 mEq/L; potassium 3.5–5.0 mEq/L; a normal cortisol rhythm (high AM, low PM).
Words to know: cortisol = the stress steroid that raises sugar/BP and calms inflammation; aldosterone = the mineralocorticoid that keeps Na⁺/water and dumps K⁺; ACTH = the pituitary signal to make cortisol; glucocorticoid = cortisol-type drug; mineralocorticoid = aldosterone-type drug.
Bottom line: Cortisol turns up sugar, anti-inflammation, and pressure, and aldosterone keeps salt/water in and potassium out — so once you know "cortisol/aldosterone = high sugar, high salt, high BP, low K⁺," you can predict every finding in both diseases just by asking too much (Cushing) or too little (Addison)?
💥 Step 2 — What Broke
The break: Both diseases hit the same adrenal cortex hormones; they differ on one axis — direction (too much vs too little) and how much of the cortex is involved. Cushing overloads cortisol; Addison loses cortisol AND aldosterone together.
Shared mechanism (true for both):
- The cortisol axis is deranged — because the adrenal cortex from Step 1 is either over-producing or under-producing. This matters because cortisol sets sugar, salt/pressure, and immune tone, so any derangement shows up in exactly those systems.
How each one diverges:
Cushing
- too MUCH cortisol — because the source is pumping out excess glucocorticoid → sugar, salt/water, and BP all get pushed up while protein/bone/skin get broken down, giving the puffed-up, propped-up, thin-skinned body.
Addison
- too LITTLE cortisol AND aldosterone — because the entire adrenal cortex is destroyed (primary insufficiency), so BOTH the glucocorticoid and the mineralocorticoid are lost → sugar, salt, and BP all fall while potassium climbs, and low cortisol drives ACTH sky-high.
Causes & Risk Factors
- Shared: any disturbance of the ACTH–cortisol axis; middle-aged adults; women more often for Cushing.
Cushing
- #1 cause is exogenous steroids (chronic prednisone) — because giving glucocorticoid IS cortisol excess. Endogenous causes, in order: pituitary ACTH adenoma (= Cushing DISEASE), then adrenal tumor, then ectopic ACTH (e.g., small-cell lung cancer).
Addison
- #1 cause is autoimmune destruction of the adrenal cortex — because the body attacks its own gland until it can't make cortisol or aldosterone. Other causes: TB, adrenal hemorrhage, and — the trap — abrupt withdrawal of chronic steroids (the suppressed adrenals can't restart).
Bottom line: Same organ, opposite direction — Cushing = cortisol flooding in (± spillover onto salt-retention); Addison = cortisol AND aldosterone draining out — and Cushing is often a drug you gave, while Addison is often the gland destroying itself.
👀 Step 3 — What the Nurse Sees (Shared vs Split)
🟰 Shared — true for both
- Abnormal blood glucose — Why: because cortisol sets blood sugar; only the direction depends on excess vs deficiency. → Nurse: monitor glucose in both patients.
- Blood-pressure derangement — Why: because cortisol/aldosterone set vascular tone and salt/water. → Nurse: trend BP in both, expecting opposite directions.
- Sodium AND potassium disturbance — Why: because the salt-retaining/K⁺-dumping action is altered in both. → Nurse: watch the Na⁺/K⁺ panel in both — they'll read opposite.
🔀 What's different — by condition
Cushing (too much cortisol)
- Infection with blunted signs (fever/pus masked) — Why: because cortisol suppresses immunity and the inflammatory response. → Nurse: the quiet killer — screen aggressively; a "well-looking" Cushing patient can be septic.
- Hyperglycemia — Why: because cortisol drives gluconeogenesis and insulin resistance. → Nurse: monitor glucose; may need insulin even without known diabetes.
- Hypertension + fluid retention — Why: because cortisol has aldosterone-like salt-and-water holding activity. → Nurse: monitor BP and daily weight.
- HYPOkalemia + hypernatremia — Why: because that same salt-retention holds Na⁺ and dumps K⁺. → Nurse: "high everything except low K⁺" — watch for weakness/arrhythmia.
- Moon face, buffalo hump, truncal obesity with thin wasted extremities — Why: because cortisol redistributes fat centrally while breaking down limb muscle. → Nurse: the classic "lemon on toothpicks" habitus.
- Purple striae, thin fragile skin, easy bruising, poor wound healing — Why: because cortisol breaks down collagen and protein. → Nurse: skin-tear precautions; wounds heal slowly.
- Osteoporosis / fracture risk — Why: because cortisol pulls calcium out of bone. → Nurse: fall and fracture precautions.
- Hirsutism, acne, and mood swings/psychosis — Why: because excess adrenal androgens grow hair and steroid excess destabilizes mood. → Nurse: supporting cues; offer psych support.
Addison (too little cortisol AND aldosterone)
- Hypotension → shock — Why: because losing both cortisol and aldosterone strips vascular tone AND volume. → Nurse: the worst-case (Addisonian crisis) — orthostatic precautions, IV access ready.
- HYPERkalemia — Why: because without aldosterone the kidney can't excrete K⁺. → Nurse: watch the ECG (peaked T waves, arrhythmia).
- Hyponatremia + salt craving — Why: because lost aldosterone dumps Na⁺ and water. → Nurse: expect low Na⁺; the patient may crave salt.
- Hypoglycemia — Why: because without cortisol there's no gluconeogenesis to hold sugar up. → Nurse: check glucose; give dextrose in crisis.
- Bronze HYPERpigmentation of skin, creases, and mucous membranes — Why: because low cortisol drives ACTH sky-high, and ACTH shares a precursor with melanocyte-stimulating hormone. → Nurse: the discriminating tell — present only in PRIMARY Addison, never in Cushing.
- Fatigue, profound weakness, weight loss — Why: because there's no cortisol to fuel metabolism or the stress response. → Nurse: a wasting, exhausted patient.
- Nausea, anorexia, vomiting, diarrhea — Why: because cortisol deficiency disrupts GI function. → Nurse: supporting cues that worsen the volume loss.
Labs & Diagnostics — Know These Numbers
- Serum cortisol — HIGH in Cushing vs LOW in Addison because the source is over- vs under-producing. → Nurse: the anchor lab; direction sets everything else.
- Potassium (3.5–5.0) — LOW in Cushing vs HIGH in Addison because salt-retention is over- vs under-active. → Nurse: hold K⁺-wasters/watch ECG in Cushing; hyperkalemia/ECG precautions in Addison.
- Sodium (135–145) — HIGH in Cushing vs LOW in Addison because water/salt is held vs lost. → Nurse: interpret in the direction the disease predicts.
- Glucose (70–110) — HIGH in Cushing vs LOW in Addison because cortisol raises sugar. → Nurse: treat hyperglycemia in Cushing; give dextrose in Addisonian crisis.
- Confirmatory tests — Cushing: dexamethasone suppression test (cortisol fails to suppress) + late-night salivary cortisol; Addison: ACTH stimulation test (cortisol fails to rise). → Nurse: know which test names which disease.
🔑 Master Comparison — Cushing vs Addison
| Feature | Cushing (too much cortisol) | Addison (too little cortisol + aldosterone) |
|---|---|---|
| Cortisol level | High | Low |
| Sodium | High | Low |
| Potassium | Low | High |
| Glucose | High | Low |
| Blood pressure | High (HTN) | Low (→ crisis/shock) |
| Skin | Thin, bruises, purple striae | Bronze hyperpigmentation |
| Weight / body | Weight gain: moon face, buffalo hump, truncal fat, thin limbs | Weight loss, wasting, fatigue |
| The emergency | Masked infection/sepsis, hyperglycemic + hypertensive crisis (slow, hidden) | Addisonian crisis: shock + hyperkalemia + hypoglycemia (acute, fast) |
| Treatment direction | Remove the source / taper excess steroids (never stop abruptly) | Replace glucocorticoid + mineralocorticoid for life; stress-dose when ill |
Bottom line: Cushing = everything HIGH (cortisol, Na⁺, glucose, BP, weight) EXCEPT low K⁺, with thin/bruised/striae skin, and it kills slowly by hidden infection; Addison = everything LOW (cortisol, Na⁺, glucose, BP, weight) EXCEPT high K⁺, with BRONZE skin, and it crashes fast into shock.
🩺 Step 4 — What We Do (Shared vs Split)
Care hook: Both are fixed by getting cortisol back to normal — but the DIRECTION of the fix is opposite (dial Cushing DOWN, replace Addison UP), and the shared trap is the same for both: you never yank steroids away suddenly.
Shared care (true for both):
- Correct the cortisol level toward normal and monitor glucose, Na⁺, K⁺, and BP (Circulation) — because these are the systems cortisol/aldosterone control, and they're deranged in both.
- Never stop glucocorticoids abruptly (Safety) — because sudden cortisol loss precipitates an Addisonian crisis in ANY steroid-dependent patient (the Cushing patient on steroids AND the Addison patient on replacement).
- Protect from infection and monitor for it carefully (Infection) — because cortisol excess masks infection in Cushing, and physiologic stress from infection can crash the Addison patient.
- Wear/carry medical alert + patient teaching on illness rules (Safety) — because both patients need a plan for the day they get sick or need surgery.
Where care diverges — by condition:
Cushing
- remove or reduce the source — because the problem is excess. Taper/withdraw exogenous steroids slowly; surgically remove a pituitary adenoma (transsphenoidal) or adrenal tumor; give adrenal-enzyme blockers (e.g., ketoconazole, metyrapone) when surgery isn't possible.
Addison
- lifelong replacement — because the problem is deficiency. Give a glucocorticoid (hydrocortisone) PLUS a mineralocorticoid (fludrocortisone), and STRESS-DOSE (2–3× the dose) during illness, surgery, or major stress — because the missing gland can't ramp up on its own.
Medications
Cushing
- Ketoconazole / metyrapone (adrenal enzyme inhibitors) → Cushing (medical control) → because they block cortisol synthesis → monitor for adrenal insufficiency (over-suppression flips them toward Addison).
Addison
- Hydrocortisone (glucocorticoid) → replacement in Addison, and IV rescue in Addisonian crisis → because it restores the missing cortisol → teach never to skip a dose and to stress-dose when ill.
- Fludrocortisone (mineralocorticoid) → Addison only → because it replaces aldosterone to hold Na⁺/water and excrete K⁺ → watch for edema/HTN/hypokalemia if over-replaced.
- IV normal saline + IV dextrose → Addisonian crisis → because they reverse the hypotension/shock and hypoglycemia → titrate to BP and glucose.
🚨 Complications to Prevent / Catch Early
Cushing
- Masked infection / sepsis — watch for: subtle mental-status change, tachycardia, or rising lactate WITHOUT fever (Infection) — because cortisol excess hides the classic signs. (Cushing.)
- Osteoporotic fracture / skin breakdown — watch for: falls, back pain, skin tears (Safety) — because cortisol excess weakens bone and skin. (Cushing.)
Addison
- Addisonian crisis — watch for: worsening hypotension, hyperkalemia, hypoglycemia, vomiting, fever after a missed dose or during illness (Circulation) — because unreplaced cortisol collapses vascular tone. (Addison; also any patient whose steroids were stopped abruptly.)
Bottom line: The single shared priority is normalizing cortisol without ever stopping steroids abruptly — and the direction flips by disease: Cushing you dial DOWN (remove source / taper), Addison you replace UP for life and stress-dose when sick.
🔗 Connection Map (normal → broken → see → do)
| Member | 🟢 Normal (shared) | 💥 Broke | 👀 See (the tell) | 🩺 Do |
|---|---|---|---|---|
| Cushing | Cortisol raises sugar/salt/BP, dumps K⁺ | Too MUCH cortisol (± salt spillover) | High glucose/Na⁺/BP, low K⁺, moon face, purple striae, thin skin | Remove source / taper; never stop abruptly; guard against masked infection |
| Addison | Cortisol + aldosterone hold sugar/salt/BP, dump K⁺ | Too LITTLE cortisol AND aldosterone | Low glucose/Na⁺/BP, high K⁺, bronze skin, weight loss, salt craving | Replace glucocorticoid + mineralocorticoid for life; stress-dose; IV hydrocortisone in crisis |
🎯 On the Exam
Don't Confuse
| Don't confuse… | The tell that flips it |
|---|---|
| Cushing vs Addison (the labs) | Potassium: low K⁺ (Cushing) vs high K⁺ (Addison) |
| Cushing vs Addison (the skin) | Thin, bruised, purple striae (Cushing) vs bronze hyperpigmentation (Addison) — the one thing that isn't a simple mirror |
| Cushing vs Addison (the emergency) | Slow, masked infection (Cushing) vs acute shock: Addisonian crisis (Addison) |
| Cushing vs Addison (the fix) | Taper/remove the excess (Cushing) vs replace + stress-dose the deficiency (Addison) |
Escalate Now
- Chronic steroids stopped abruptly + patient looks sick → impending adrenal crisis. (Any steroid-dependent patient.)
Cushing
- Cushing patient with no fever but rising WBC/lactate or new confusion → masked sepsis. (Cushing.)
- Very high glucose + hypertensive emergency → hyperglycemic/hypertensive crisis. (Cushing.)
Addison
- BP crashing with hyperkalemia and hypoglycemia → Addisonian crisis. (Addison.)
Per-Condition Fingerprint
Cushing
too MUCH cortisol → puffed up & propped up: high sugar/salt/BP, low K⁺, thin bruised skin with purple striae; kills slowly by masked infection.
Addison
too little cortisol AND aldosterone → wasted & dropped out: low sugar/salt/BP, high K⁺, bronze skin, salt craving; crashes fast into Addisonian shock.