Carcinoid syndrome
A cluster of symptoms — flushing, diarrhoea and sometimes wheezing — caused by a neuroendocrine (carcinoid) tumour releasing serotonin and other chemicals into the blood. It usually appears once the tumour has spread to the liver, and is diagnosed with urine 5-HIAA and chromogranin A.
What it is
Carcinoid syndrome is caused by a carcinoid tumour — a slow-growing neuroendocrine tumour, most often in the small intestine, appendix or lung — that secretes hormone-like chemicals, chiefly serotonin. Under normal circumstances the liver breaks these chemicals down before they reach the general circulation, so a small gut tumour causes no such symptoms. The syndrome typically appears only once the tumour has spread to the liver, where the chemicals bypass this breakdown and flood the bloodstream. The hallmark features are episodic flushing (sudden reddening of the face and neck), diarrhoea, and sometimes wheezing and abdominal cramps. Attacks can be triggered by stress, alcohol or certain foods. Over years, the chemicals can damage heart valves (carcinoid heart disease). Diagnosis rests on measuring the breakdown product of serotonin, 5-HIAA, in a 24-hour urine collection, and chromogranin A in the blood, together with imaging to locate the tumour. The tumours themselves are often slow-growing, and both the tumour and the symptoms can be treated — medicines such as somatostatin analogues control the flushing and diarrhoea, and surgery or other therapies address the tumour — so recognising the pattern matters.
Key lab markers
- Urine 5-HIAA (24-hour) — the key test; raised from excess serotonin (needs dietary preparation to avoid false results).
- Chromogranin A — a general neuroendocrine-tumour marker, used for diagnosis and monitoring.
- Electrolytes — diarrhoea can disturb them.
- NT-proBNP / heart assessment — screens for carcinoid heart valve disease over time.
Symptoms
- Episodic flushing of the face and neck
- Diarrhoea, sometimes with abdominal cramps
- Wheezing or breathlessness
- Flushing triggered by stress, alcohol or certain foods
- A fast heartbeat or drop in blood pressure during attacks
- Over years, symptoms of heart valve disease (breathlessness, swelling)
Related symptoms
When to discuss with a doctor
See a doctor about recurrent, unexplained flushing — especially if it comes with diarrhoea, wheezing or is triggered by alcohol or food — as this pattern, while usually due to commoner causes, is the classic picture of carcinoid syndrome and warrants investigation. Because the syndrome usually reflects a tumour that has already spread to the liver, timely diagnosis and specialist (oncology / endocrinology) management matter, both to treat the tumour and to control symptoms and protect the heart. Mediora.AI can surface the raised 5-HIAA and chromogranin A pattern that suggests carcinoid syndrome from your results and flag it for review, but confirming the diagnosis, locating the tumour and planning treatment is a specialist assessment — the interpretation belongs with your doctor.