Pheochromocytoma
Endocrinology
Illness script · Endocrinology
Pheochromocytoma
Catecholamine-secreting tumor of adrenal medulla chromaffin cells causing episodic or sustained hypertension and sympathetic surges.
This illness script for Pheochromocytoma covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Peak incidence 40–60 years; equal sex distribution
- Associated with MEN2A/2B (RET mutation), MEN2B, VHL disease, NF1
- ~10% bilateral, ~10% malignant, ~10% extra-adrenal (paraganglioma)
- Familial cases often younger at presentation
- Rule of 10s: 10% bilateral, hereditary, malignant, extra-adrenal
02
Presentation
- Classic triad: episodic headache, diaphoresis, palpitations
- Hypertension (sustained or paroxysmal) — resistant to standard therapy
- Attacks triggered by stress, anesthesia, tumor manipulation, tyramine-rich foods, or medications (opioids, TCAs, glucagon)
- Pallor (not flushing) during attacks; orthostatic hypotension between attacks
- Weight loss, anxiety, tremor; glucose intolerance from catecholamine effect
- Hypertensive crisis can cause MI, stroke, or pulmonary edema
03
Pathophysiology
- Chromaffin cells of adrenal medulla autonomously secrete epinephrine, norepinephrine, dopamine
- Catecholamine excess → α1-mediated vasoconstriction → severe hypertension
- Episodic release causes paroxysmal crises; large tumors may secrete continuously
- Tumor may also release neuropeptide Y, VIP, causing variable clinical phenotype
04
Diagnostics
- First-line: 24-hour urine fractionated metanephrines & catecholamines (high sensitivity)
- Alternatively: plasma free metanephrines (high sensitivity; best for high-risk/hereditary patients)
- CT abdomen/pelvis for localization after biochemical confirmation (imaging first risks false positives)
- MIBG scintigraphy or DOTATATE PET for metastatic/extra-adrenal disease
- Key pitfall: many drugs (TCAs, decongestants, levodopa) cause false-positive catecholamine results
05
Management
- Alpha-blockade FIRST (phenoxybenzamine or doxazosin) — mandatory before any beta-blocker
- Beta-blocker added ONLY after adequate alpha-blockade to prevent unopposed α-vasoconstriction crisis
- Liberal salt/fluid intake after alpha-blockade to expand volume (prevents post-op hypotension)
- Definitive treatment: laparoscopic adrenalectomy
- Surgical manipulation risk: intraoperative hypertensive crisis managed with IV phentolamine or nitroprusside
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Essential hypertension
Pheochromocytoma causes episodic paroxysmal crises with headache-diaphoresis-palpitation triad; essential HTN is sustained without dramatic surges.
Carcinoid tumor
Carcinoid causes flushing (not pallor) and diarrhea; pheochromocytoma causes pallor, palpitations, and markedly elevated metanephrines.
Panic disorder
Panic attacks lack hypertension severity and have normal plasma/urine metanephrines; pheo crises are biochemically confirmable.
Paraganglioma
Paraganglioma is extra-adrenal chromaffin tumor (same biochemistry) but more often hereditary, malignant, and located along sympathetic chain.
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Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.