Lecture Notes: Pheochromocytoma

Overview

• Pheochromocytoma: A condition due to a catecholamine-secreting tumor formed by chromaffin cells within the adrenal medulla.
• Location: Tumor located in the adrenal medulla, which is the inner part of the adrenal gland sitting atop the kidneys.
• Malignancy: 10% of pheochromocytomas are malignant.
• Comparison: Similar presentation to paragangliomas, which originate from sympathetic nervous tissue.

Etiology

• Idiopathic: Most cases are without a known cause.
• Genetic Component: Family history may indicate potential for pheochromocytoma.
  • Associated genetic conditions: MEN 2A, MEN 2B, Von Hippel-Lindau syndrome.

Pathophysiology

• Chromaffin Cells: Normally produce catecholamines like norepinephrine and epinephrine.
• Tumor Effects: Leads to hypersecretion of norepinephrine, epinephrine, and smaller dopamine amounts.
• Adrenergic Receptors Affected:
  • Alpha 1: Causes vasoconstriction and increased blood pressure.
  • Beta 1: Increases cardiac output, heart rate, and stroke volume.
  • Beta 2: Involved in smooth muscle relaxation in the respiratory system.

Signs and Symptoms

• Classic Triad:
  1. Episodic pounding headache
  2. Palpitations and tachycardia
  3. Diaphoresis
• Other Symptoms: Orthostatic hypotension, weight loss, polyuria, polydipsia, constipation, hyperglycemia, insulin resistance, papilledema, paroxysmal hypertension, cardiac issues.
• Symptom Triggers: Stress, exertion, anesthesia, abdominal pressure, tyramine-containing foods (e.g., cheese, wine).

Diagnosis

• Initial Steps:
  • Discontinue interfering medications, particularly tricyclic antidepressants.
• Investigations:
  • 24-hour urine fractionated metanephrines and catecholamines.
  • Plasma fractionated metanephrines (sample after 30 minutes supine rest).
• Imaging: If catecholamines are elevated, use adrenal or abdominal MRI/CT.
  • For tumors >10 cm, use I-123 MIBG scan or whole-body MRI.

Genetic Testing

• Associated with MEN 2 syndromes and Von Hippel-Lindau syndrome.
• Tests: RET proto-oncogene, VHL mutation.

Treatment

• Surgical Resection: Often curative.
  • Preoperative Steps:
    1. Alpha-adrenergic blockade (10-14 days before surgery).
    2. Beta-adrenergic blockade.
  • Medications:
    • Alpha blockade: Phenoxybenzamine, daily blood pressure monitoring, high-sodium diet.
    • Beta blockade: Propranolol, then long-acting beta blockers.
  • Alternative Management: Catecholamine synthesis inhibitor like Metyrosine if others are ineffective.

Conclusion

• Comprehensive management involves recognizing symptoms, discontinuing interfering medications, proper diagnostic testing, and careful preoperative preparation and surgical intervention.
• Further education and content available on endocrinology topics.