Carcinoid syndrome: Mechanism of action

Carcinoid tumors are rare neuroendocrine tumors which originate most often in the bowel, less commonly in the lungs, and rarely in the reproductive tract.

Carcinoid syndrome will occur in a small percentage of patients  (~10%).

Symptoms include:

• Facial flushing
• Abdominal cramps and diarrhea
• Bronchospasm
• Palpitations
• Shortness of breath

MECHANISM: Tumor-derived 5-HTP metabolites, such as serotonin, akinins, and prostaglandins entering systemic circulation cause these symptoms.

Carcinoid syndrome is usually seen in patients with lung primaries or liver metastases from bowel primary carcinoid tumour that escape the enterohepatic circulation and enter directly into the systemic blood supply.

Otherwise, if the mediators are released from a primary bowel carcinoid tumour, they are released into portal venous blood supply and are metabolized by the liver.

REFERENCES

1. The MD Anderson Manual of Medical Oncology, 3e. Chapter 26: Neuroendocrine Tumors. Daniel M. Halperin; James C. Yao