Short answer · Medically reviewed summary · Last updated: 2026-05-08
Carcinoid syndrome is a collection of symptoms caused by rare, slow-growing neuroendocrine tumors (NETs) that secrete hormones—most notably serotonin—into the bloodstream. While these tumors often originate in the digestive tract or lungs, Carcinoid syndrome specifically occurs when these substances bypass the liver's filtering system, typically due to metastasis, leading to systemic effects like flushing and diarrhea. How does Carcinoid syndrome affect the body? In a healthy body, the liver breaks down hormones produced by neuroendocrine tumors.
What is Carcinoid Syndrome
What is Carcinoid Syndrome? Plain-language, medically reviewed definition plus the lived reality told by patients.
Carcinoid syndrome is a collection of symptoms caused by rare, slow-growing neuroendocrine tumors (NETs) that secrete hormones—most notably serotonin—into the bloodstream. While these tumors often originate in the digestive tract or lungs, Carcinoid syndrome specifically occurs when these substances bypass the liver's filtering system, typically due to metastasis, leading to systemic effects like flushing and diarrhea.
How does Carcinoid syndrome affect the body?
In a healthy body, the liver breaks down hormones produced by neuroendocrine tumors. However, in Carcinoid syndrome, these hormones enter the systemic circulation, causing widespread symptoms. The most common indicators include episodic skin flushing, chronic watery diarrhea, wheezing, and, over time, potential damage to the heart valves (carcinoid heart disease). Because Carcinoid syndrome involves the endocrine system, it can affect multiple organ systems simultaneously, often leading to a complex clinical picture that requires specialized care.
How common is Carcinoid syndrome?
Carcinoid syndrome is rare, occurring in approximately 8% to 10% of patients diagnosed with neuroendocrine tumors. While neuroendocrine tumors themselves are becoming more frequently diagnosed due to improved imaging, the prevalence of symptomatic Carcinoid syndrome remains low. It most commonly affects adults between the ages of 50 and 60, though it can occur at any age, with no significant difference in distribution between genders.
What are the key characteristics of Carcinoid syndrome?
Distinguishing Carcinoid syndrome from other gastrointestinal or respiratory conditions is critical for effective management. Key features include:
- Episodic flushing: Often triggered by stress, alcohol, or certain foods.
- Secretory diarrhea: Frequent, watery stools that do not resolve with fasting.
- Hormonal biomarkers: Elevated levels of 5-HIAA in 24-hour urine tests.
- Systemic impact: Potential for fibrotic heart valve thickening (carcinoid heart disease).
Next steps
- Consult an endocrinologist or oncologist specializing in neuroendocrine tumors.
- Request a 24-hour urine 5-HIAA test to confirm hormonal activity.
- Connect with the 49 members of the DiseaseMaps.org community who are navigating life with Carcinoid syndrome.
- Discuss potential treatments, such as somatostatin analogs, with your care team.
Medical disclaimer: This content is for informational purposes only and does not constitute medical advice; always consult with a qualified healthcare professional regarding your specific diagnosis and treatment plan.
References
- NIH Genetic and Rare Diseases (GARD) Information Center - Carcinoid Syndrome
- Orphanet: Neuroendocrine tumors of the gastrointestinal tract
- The Neuroendocrine Cancer Awareness Network (NCAN)
- PubMed: Clinical presentation and management of carcinoid syndrome
