# Carcinoid Syndrome Clinical Features and Medical Management > Carcinoid syndrome for NEET-PG Medicine: serotonin-mediated flushing and diarrhoea, 5-HIAA testing, right-sided heart lesions and octreotide symptom control. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/carcinoid-syndrome - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-08 - Last updated: 2026-10-08 - Reference basis: Harrison's Principles of Internal Medicine; Sleisenger and Fordtran's Gastrointestinal and Liver Disease; Robbins and Cotran Pathologic Basis of Disease - How to cite: "Carcinoid Syndrome Clinical Features and Medical Management", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/carcinoid-syndrome ## Direct answer Carcinoid syndrome is a set of flushing, diarrhoea, bronchospasm and cardiac lesions caused by systemic serotonin released from a neuroendocrine carcinoid tumour, usually of midgut origin with liver metastases. It is confirmed by raised urinary 5-HIAA, and somatostatin analogues such as octreotide are the mainstay of symptom control. ## What you must remember - **Origin:** Midgut carcinoids, mainly in the ileum, cause the classic syndrome once liver metastases allow serotonin to reach the systemic circulation. - **Flushing and diarrhoea:** Facial and upper chest flushing with secretory diarrhoea are the commonest features. - **Heart:** Right-sided tricuspid regurgitation and pulmonary stenosis from fibrous plaques; the lungs normally inactivate serotonin, so left-sided lesions are unusual. - **5-HIAA:** The 24-hour urinary 5-hydroxyindoleacetic acid is the diagnostic marker; bananas, walnuts, plums, kiwi and avocado cause false positives. - **Chromogranin A:** A supportive marker of neuroendocrine tumour burden. - **Pellagra:** Tryptophan diverted to serotonin can cause niacin deficiency. - **Treatment:** Octreotide or lanreotide for symptoms; telotristat for diarrhoea not controlled by somatostatin analogues; intravenous octreotide for crisis. ## A worked case: flushing, diarrhoea and a murmur A 58-year-old woman has episodes of facial flushing, watery diarrhoea and wheezing. CT shows an ileal primary with liver metastases, and urinary 5-HIAA is raised. Echocardiography shows tricuspid regurgitation. 1. **Confirm hormonal excess:** The approach begins with urinary 5-HIAA and plasma chromogranin A, after dietary restriction of serotonin-rich foods before the urine collection, since bananas, walnuts and avocado cause false-positive results. 2. **Localise the tumour:** CT or MRI and somatostatin receptor imaging identify the primary and the metastases, and guide whether surgery or liver-directed therapy is an option. 3. **Assess the heart:** Right-sided valve disease is the most important long-term complication and needs follow-up echocardiography. 4. **Control symptoms:** Octreotide controls symptoms and also has antiproliferative effects. 5. **Plan for procedures:** Manipulation of the tumour during surgery or anaesthesia can trigger a carcinoid crisis, so octreotide cover is planned in advance. Examiners often ask about this sequence in vignettes, so the order matters. ## Where the exam tries to catch you Carcinoid questions turn on where the serotonin goes and which test is misleading. - **Trap:** placing the heart lesion on the left — **Correct:** the lungs inactivate serotonin, so left-sided lesions are unusual unless the tumour is bronchial or a shunt is present. - **Trap:** assuming every small bowel carcinoid causes the syndrome — **Correct:** a small bowel primary without liver metastases generally does not, because the liver clears serotonin before it reaches the systemic circulation. - **Trap:** accepting a raised 5-HIAA without checking the diet — **Correct:** bananas, walnuts, plums, kiwi and avocado cause false-positive results, so a dietary cause must be recognised first. - **Trap:** overlooking pellagra — **Correct:** tryptophan is diverted to serotonin and niacin falls, an easily missed feature. ## Frequently asked questions ### Which urinary test confirms carcinoid syndrome? A 24-hour urinary 5-hydroxyindoleacetic acid level confirms carcinoid syndrome, because 5-HIAA is the breakdown product of serotonin. Foods such as bananas, walnuts and avocado are restricted before the test, since they cause false-positive results. ### Why does carcinoid syndrome cause right-sided heart disease? Carcinoid syndrome causes right-sided heart disease because serotonin released into the systemic circulation escapes lung inactivation and deposits fibrous plaques on the tricuspid and pulmonary valves. Left-sided lesions are uncommon unless the origin is bronchial or a shunt is present. ### Which drug is used for first-line control of carcinoid syndrome symptoms? Somatostatin analogues such as octreotide or lanreotide are first-line for carcinoid syndrome symptom control, reducing flushing and diarrhoea. Telotristat ethyl is added for diarrhoea that persists despite somatostatin analogues. ### What is a carcinoid crisis and how is it treated? A carcinoid crisis is a sudden episode of severe flushing, hypotension and bronchospasm, often triggered by surgery, anaesthesia or tumour manipulation. It is treated with intravenous octreotide and supportive measures, and cover is given before any procedure that may trigger it. ### Why does a small bowel carcinoid without liver metastases often not cause carcinoid syndrome? A small bowel carcinoid without liver metastases often does not cause carcinoid syndrome, because the liver normally metabolises serotonin before it reaches the systemic circulation. Syndrome usually appears only when metastases or a shunt bypass hepatic clearance.