Pheochromocytoma vs. Carcinoid – What’s the Difference??

by | Sep 29, 2015 | Cardiology, Science |

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.

 

Carcinoid

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

 

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Pheochromocytoma

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.

 

References

1. Patel C, Mathur M, Escarcega RO, Bove AA.  Carcinoid heart disease: current understanding and future directions.   Am Heart J. 2014 Jun;167(6):789-95.

2. Dobson R, Burgess MI, Pritchard DM, Cuthbertson DJ.  The clinical presentation and management of carcinoid heart disease.  Int J Cardiol. 2014 Apr 15;173(1):29-32.

3. Lenders JW1, Eisenhofer G, Mannelli M, Pacak K.  Phaeochromocytoma.  Lancet. 2005 Aug 20-26;366(9486):665-75.

4. Pappachan JM1, Raskauskiene D, Sriraman R, Edavalath M, Hanna FW.  Diagnosis and management of pheochromocytoma: a practical guide to clinicians.Curr Hypertens Rep. 2014 Jul;16(7):442.

 

 

 

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