Carcinoid syndrome

Page most recently updated 7 September 2026

This page focuses on the reported psychiatric associations, which may be the initial presenting manifestation, and on other clinical features that may assist the psychiatrist or primary care physician in identifying the underlying diagnosis, considered through the lenses of the diagnostic lenses framework.

Carcinoid syndrome is a paraneoplastic syndrome caused by the secretion of serotonin and other vasoactive substances by neuroendocrine tumours, most commonly arising in the ileum and metastasizing to the liver.

It can present with psychiatric features such as anxiety, depression, cognitive changes, and, rarely, psychotic symptoms. Neuropsychiatric manifestations may be related to the systemic effects of the neuroendocrine tumour or to niacin (vitamin B3) deficiency (pellagra), which can occur in patients with marked serotonin production.

Other characteristic features include episodic flushing, typically involving the face, neck, and upper chest; chronic secretory diarrhoea; abdominal pain or cramping; and bronchospasm with wheezing. Hepatic metastases are very common in carcinoid syndrome but may be clinically occult, without hepatomegaly or LFT abnormalities. A distinctive complication is carcinoid heart disease, which predominantly affects the right-sided cardiac valves and can progress to right-sided heart failure. Carcinoid crisis is a potentially life-threatening acute complication characterized by severe flushing, marked blood-pressure fluctuations, bronchospasm, diarrhoea, and haemodynamic instability.

From a multisystemic lens perspective, clinical features in other body systems include (but are not limited to):

  • Cardiovascular: Carcinoid heart disease, characterized predominantly by fibrotic thickening and dysfunction of the tricuspid and pulmonary valves, resulting in regurgitation and/or stenosis and potentially right-sided heart failure. Episodic tachycardia and blood-pressure fluctuations may accompany the syndrome, while severe haemodynamic instability occurs during carcinoid crisis.

  • Respiratory: Episodic bronchospasm, wheezing, and dyspnoea.

  • Gastrointestinal: Chronic secretory diarrhoea, often profuse; abdominal cramping or pain; nausea; and, with more advanced disease, weight loss and nutritional deficiencies.

  • Dermatologic: Episodic flushing of the face, neck, and upper chest, typically reddish-brown or bright red and often short-lived. Chronic disease may be associated with pellagrous dermatitis from niacin deficiency.

Early diagnosis is important to identify the underlying neuroendocrine tumour, initiate treatment to control hormone-mediated symptoms and tumour activity, reduce the risk of serious complications such as carcinoid heart disease and carcinoid crisis, and address nutritional deficiencies and other consequences of chronic diarrhoea, thereby improving prognosis and quality of life.

Selected references and further reading — Multisystemic lens

Cardinal RN, Bullmore ET. The diagnosis of psychosis. Cambridge: Cambridge University Press; 2011.

Sachdev PS, Keshavan MS, editors. Secondary schizophrenia. Cambridge: Cambridge University Press; 2010.

Levenson JL, editor. The American Psychiatric Association Publishing textbook of psychosomatic medicine and consultation-liaison psychiatry. 3rd ed. Washington (DC): American Psychiatric Association Publishing; 2019.

Stern TA, Beach SR, Smith FA, Freudenreich O, Vranceau AM, Fava M, editors. Massachusetts General Hospital handbook of general hospital psychiatry. 8th ed. Philadelphia: Elsevier; 2025.

Arciniegas DB, Yudofsky SC, Hales RE, editors. The American Psychiatric Association Publishing textbook of neuropsychiatry and clinical neurosciences. 6th ed. Washington (DC): American Psychiatric Association Publishing; 2018.

Agrawal N, Faruqui R, Bodani M, editors. Oxford textbook of neuropsychiatry. Oxford: Oxford University Press; 2020.

Boland R, Verduin M, editors. Kaplan and Sadock's comprehensive textbook of psychiatry. 11th ed. Philadelphia: Wolters Kluwer; 2024.

Loscalzo J, Fauci AS, Kasper DL, Hauser SL, Longo DL, Jameson JL, editors. Harrison's principles of internal medicine. 22nd ed. New York: McGraw Hill; 2025.