Pheochromocytoma vs. Carcinoid – What’s the Difference??
Two neuroendocrine tumors affecting the cardiovascular system and often get confused are carcinoid and pheochromocytoma. I thought I would include a brief primer on the two, because both secrete some degree of catecholamines; however both are completely different in management and treatment.
Primarily secretion of serotonin (5-HT) >> catecholamines
Serotonin release: flushing, diarrhea, bronchospasm/wheezing, Carcinoid heart disease
Tumors found in midgut enterochromaffin cells: small intestines, cecal, ascending colon, bronchopulmonary. Happens in 5th to 7th decade of life usually.
Serotonin cycle in Carcinoid: tryptophan –(trp-OH-ase)—> 5OH-tryptophan —(AADC)–> serotonin —(MAO)–> 5-HIAA
The serotonin metabolite 5-HIAA is excreted in urine and is used to diagnose Carcinoid. 24-hour urine 5-HIAA is the most important clue to Carcinoid syndrome.
Carcinoid heart disease: tricuspid regurgitation with TV “frozen” midway, pulmonary stenosis > regurgitation, R>L HD, increased PFO incidence, prominent early large “v” wave in jugular veins.
False-positive Ur-5-HIAA: high tryptophan diet
False-negatve Ur-5-HIAA: levodopa therapy for Parkinson’s
Medical therapy for Carcinoid: Octreotide (somatostatin analogue), reduces vasoactive peptide secretion.
Surgical therapy for non-metastatic Carcinoid: surgical resection
Primarily catecholamine release >> serotonin release.
Pheo catecholamines are released from the adrenal medulla (85%) or extra-adrenal chromaffin tissue (15%)
Classic symptoms of Pheo: episodic hypertension, palpitations, sweating, headache, orthostatic BP, vasoconstriction, anxiety/panic.
Metabolic Pheo Sequelae: hyperglycemia, lactic acidosis, weight loss
Associated with genetic conditions: MEN2, VHL, NF1, and SDH B/D
Remember, MEN2 = MTC, Pheo, PTH (2a) or mucosa neuroma (2b)
Pheo (bio)chemical diagnosis: plasma-free metanephrines, urinary fractionated metanephrines
- Reason: catecholamines produced by pheo are metabolized to metanephrines, independent of quantity of pheo release
Pheo imaging: CT/MRI, I123-MIBG imaging
Surgical Pheo therapy: laparoscopic tumor removal
Surgical Pre-Op for Pheo: alpha blockade with phenoxybenzamine 10 mg bid (titrate up to 1 mg/kg) prior to beta blockade with propranolol 40 mg tid
So there you have it, two neuroendocrine tumors causing CVD. Stay tuned for more differential diagnoses.
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