Carcinoid syndrome
D E FI N I T ION
Constellation of symptoms caused by systemic release of humoral factors
(biogenic amines, polypeptides, prostaglandins) from carcinoid tumours.
AETIOLOGY
Carcinoid tumours are slow-growing neuroendocrine tumours mostly derived
from serotonin-producing enterochromaffin cells. They produce secretory products
such as serotonin, histamine, tachykinins, kallikrein and prostaglandin. May be classified into
fore-, mid- or hindgut tumours. 75–80%of patients with the carcinoid syndrome have small
bowel carcinoids. Common sites for carcinoid tumours include appendix and rectum, where
they are often benign and non-secretory. Also found in other parts of large intestine,
stomach, thymus, bronchus and other organs. Hormones released into the portal circulation
are metabolized in the liver. Thus symptoms typically do not appear until there are hepatic
metastases (resulting in the secretion of tumour products into the hepatic veins), or release
into the systemic circulation from bronchial or extensive retroperitoneal tumours.
E P IDEMIOLOGY
Rare, annual UK incidence is one in 1 000 000. Asymptomatic carcinoid
tumours are more common and may be an incidental finding after rectal biopsy or
appendectomy. Ten percent of patients with multiple endocrine neoplasia (MEN) type 1
have carcinoid tumours.
H ISTORY
Paroxysmal flushing, diarrhoea, crampy abdominal pain, wheeze, sweating,
palpitations.
EXAMINA T I ON
Facial flushing, telangiectasia, wheeze.
Right-sided heart murmurs: Tricuspid stenosis, regurgitation or pulmonary stenosis.
Nodular hepatomegaly in cases of metastatic disease.
Carcinoid crisis: Profound flushing, bronchospasm, tachycardia and fluctuating blood
pressure.
INVE S T I G A T IONS
24-h urine collection: 5-HIAA levels (a metabolite of serotonin, false
positive with high intake of certain fruit/drugs e.g. bananas and avocados, caffeine,
paracetamol).
Blood: Plasma chromogranin A and B, fasting gut hormones.
CT or MRI scan: To localizes the tumour.
Radioisotope scan: Radiolabelled somatostatin analogue (e.g. indium-111 octreotide) helps
localize tumour.
Investigations for MEN-1: (see footnote to Hyperparathyroidism).
MANAGEMENT
Carcinoid crisis: Octreotide infusion, also IV antihistamine and
hydrocortisone.
Multidisciplinary approach (endocrinologists/gastroenterologists, oncologists, radiologists
and surgeons).
Advice: Avoid precipitating factors e.g. alcohol, strenuous exercise.
Somatostatin analogues (e.g. octreotide) inhibit hormone release and tumour growth.
Radiolabelled octreotide may be beneficial (receptor-targeted therapy).
Interferon-a: May be given on its own or added to long-acting somatostatin analogues if the
patient is not responding to the maximum dosage of somatostatin analogues.
Supportive: Ondansetron and cyproheptadine (5-HT antagonists) can alleviate symptoms,
rehydration (for diarrhoea), antiemetics and anti-diarrhoeal treatment (codeine,
loperamide).
Surgery: Should be considered for resectable nodal or hepatic metastasis, extraintestinal
(bronchial and ovarian) carcinoids. Small intestinal carcinoids may be resected even in the
presence of metastases, to prevent fibrosing mesenteritis. Valve surgery for symptomatic
carcinoid heart disease. A potential peri-operative carcinoid crisis should be prevented by
prophylactic treatment with octreotide
Carcinoid syndrome (continued)
Hepatic artery embolization: For patients with non-resectable multiple and hormone secreting
tumours. Two types: particle and chemoembolization.
COMPL I C A T IONS
Electrolyte imbalance (secondary to diarrhoea), metastases, bowel
obstruction (due to fibrosis near a gut primary), tricuspid and pulmonary valve stenosis with
consequent right heart failure, pellagra: dermatitis, glossitis, diarrhoea, dementia (due to
niacin deficiency caused by diversion of dietary tryptophan for the synthesis of large amounts
of serotonin).
P ROGNOS I S
Median survival is usually 5–10 years but can range up to 20 years.
Earlier detection and treatment should improve quality of life and survival.
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