Pheochromocytoma questions love to show up as “weird hypertension” with episodic symptoms—and the fastest way to lock it in on test day is a sticky mnemonic that instantly cues catecholamine surges.
The Mnemonic: “PHEO” = Pressure + Heart + Episodic + (di)Ongoing Sweats
Use PHEO to remember the classic presentation of pheochromocytoma-related HTN:
- P — Pressure spikes: paroxysmal (episodic) severe hypertension
- H — Heart racing: palpitations + tachycardia
- E — Episodic: symptoms come in spells/attacks (often minutes to hours)
- O — (di)Ongoing Sweats: diaphoresis (and often tremor/anxiety)
One-liner (the exam-ready takeaway)
Pheochromocytoma causes episodic hypertension due to catecholamine (epi/norepi) surges from a chromaffin cell tumor, classically with headaches, sweating, and palpitations.
Visual Hook: “The Adrenal Alarm Button”
Picture an adrenal gland with a big red ALARM button. When it’s pressed, it releases catecholamines in bursts:
- 🚨 Sudden BP spike
- 💓 Racing heart
- 🥵 Sweating
- 🤯 Throbbing headache
- 😰 Panic/tremor
If you see spells + the alarm symptoms, think pheo.
High-Yield USMLE Facts (Step 1 + Step 2)
What it is (and where)
- Tumor of chromaffin cells (usually adrenal medulla; can be extra-adrenal = paraganglioma)
- Secretes catecholamines: norepinephrine and epinephrine (± dopamine)
Classic symptom cluster
Often presented as the “triad”:
- Headache
- Diaphoresis
- Tachycardia/palpitations
Plus:
- Paroxysmal hypertension (can be sustained too)
- Pallor, tremor, anxiety, hyperglycemia
Triggers you may see in stems
- Surgery/anesthesia, exercise, stress, tyramine-containing foods, certain meds (e.g., metoclopramide, some anesthetics)
Diagnosis: What to Order (and Why)
Best initial biochemical tests
- Plasma free metanephrines (very sensitive)
- 24-hour urine fractionated metanephrines and catecholamines (very useful, commonly tested)
Why metanephrines? Catecholamines are metabolized continuously within the tumor, so metanephrines stay elevated even between attacks.
After biochemical confirmation
- CT/MRI of adrenals
- Consider MIBG scan if extra-adrenal disease or metastatic concern
Treatment: The “Don’t Kill the Patient” Sequence
Pre-op management (high-yield)
- Alpha-blockade first
- Phenoxybenzamine (nonselective, irreversible) is the classic answer
- Alternative: selective blocker (e.g., doxazosin)
- Then add beta-blocker only after alpha blockade
- Controls tachyarrhythmias
The reason (commonly tested)
If you give a beta-blocker first, you leave unopposed alpha-1 vasoconstriction → hypertensive crisis.
Definitive treatment
- Surgical resection (after adequate alpha blockade + volume repletion)
Associations & Genetics You Should Recognize
Pheochromocytoma is classically linked to:
- MEN 2A / MEN 2B (RET mutation; medullary thyroid carcinoma)
- Von Hippel–Lindau
- Neurofibromatosis type 1 (NF1)
Quick “Spot-It” Table (Pheo vs Other Secondary HTN)
| Cause of Secondary HTN | Key Clue | Potassium | Renin/Aldosterone | Hallmark Test |
|---|---|---|---|---|
| Pheochromocytoma | Episodic HA + sweating + palpitations | Normal | Variable | Plasma/urine metanephrines |
| Primary hyperaldosteronism | HTN + weakness/cramps | Low | Low renin, high aldo | Aldo:renin ratio |
| Renal artery stenosis | Abdominal bruit, sudden/worsening HTN | Often low/normal | High renin | Renal Doppler/CTA/MRA |
| Cushing syndrome | Central obesity, striae, glucose ↑ | Low/normal | Variable | Low-dose dex suppression / cortisol testing |
Final Memory Snap
If the vignette feels like panic attacks with dangerous BP spikes, hear the adrenal ALARM and remember:
PHEO = Pressure spikes + Heart racing + Episodic + (di)Ongoing Sweats → check metanephrines → alpha-block first.