A 50-year-old man with carcinoid syndrome presents with progressive right heart failure. Echocardiography reveals thickening and retraction of the tricuspid valve leaflets with restricted motion, resulting in both stenosis and regurgitation. The pulmonary valve is also involved. Which substance is primarily responsible for these valvular changes?
- A Histamine
- B Serotonin (5-hydroxytryptamine) ✓
- C Bradykinin
- D Prostaglandin E2
Correct answer: B. Serotonin (5-hydroxytryptamine)
Explanation
Carcinoid heart disease is caused by serotonin (5-HT) and other vasoactive substances secreted by carcinoid tumours. These substances reach the right side of the heart via the systemic circulation (liver metastases bypass hepatic metabolism), causing plaque-like fibrous deposits on the tricuspid and pulmonary valves. Left-sided involvement is rare unless there is a right-to-left shunt or bronchial carcinoid.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.