Overview
Carcinoid syndrome describes a paraneoplastic syndrome secondary to carcinoid tumours. These are rare and slow-growing neuroendocrine tumours, that release serotonin into the systemic circulation, leading to carcinoid syndrome.
Epidemiology
- Carcinoid tumours are the most common neuroendocrine tumours
- The incidence of neuroendocrine tumours is around 3 per 100,000
Risk Factors
- Family history
- Multiple endocrine neoplasia (MEN) 1
Presentation
Patients tend to present with diarrhoea and flushing due to the release of serotonin. Features include:
- Diarrhoea
- Flushing
- Bronchoconstriction
- Vague abdominal pain
- Hepatomegaly – suggests hepatic metastases
- Right-sided heart disease (e.g. tricuspid valve regurgitation), particularly if there are hepatic metastases
- Left heart disease in those with pulmonary metastases
Investigations
- Urinary 5-hydroxyindoleacetic acid (5-HIAA):
- This is the main metabolite of serotonin
- Increased levels are seen
Management
Management may involve surgery, somatostatin analogues (e.g. octreotide, which works by blocking serotonin release), chemotherapy, and radiotherapy.
Prognosis
Median survival varies on the stage of tumour development. Some studies have shown a median survival of around 11.5 years for small, localised tumours, and around 5.5 years for metastatic disease.
