- Credits
- Section Writer: Dr. Om J Lakhani
- Section Editor: Dr. Om J Lakhani
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Q: What is Carcinoid syndrome?
These are symptoms arising from hormone and amines secreted by carcinoid tumors.
Q: What are the symptoms of Carcinoid syndrome?
They are given by the mnemonic: "When having diarrhea, use the right-sided valve to flush the toilet, else the next person in would have bronchoconstriction."
Q: Which are the commonest symptoms?
Flushing and diarrhea.
Q: What are main groups of products formed by Carcinoid tumors?
Amines like serotonin, dopamine, noradrenaline; peptides like GHRH, ACTH, etc.; prostaglandins.
Q: Why do GI NETs with hepatic mets have carcinoid syndrome and not others?
Liver inactivates many of the amines produced by the GI carcinoids. Hence, without hepatic mets, the products go to portal circulation and are destroyed by liver. If there are liver mets, portal circulation is bypassed and products go directly into systemic circulation, causing symptoms. Ovarian carcinoids can produce symptoms directly because they directly drain into the systemic circulation.
**Pathophysiology **
Q: Which are some prominent products released by these tumors?
A: Serotonin, Tachykinin, Kallikrein, Prostaglandins.
Q: Why do foregut carcinoids not produce serotonin?
A: This is because they lack the enzyme Aromatic acid decarboxylase. This converts 5-hydroxytryptophan to serotonin. Hence, 5-HTP is released but not serotonin.
Q: Why do these patients develop pellagra-type features?
A: Niacin is formed from tryptophan. Hence, when a lot of tryptophan is diverted to serotonin synthesis, there is niacin deficiency. This produces pellagra.
Q: What is responsible for the diarrhea?
A: Serotonin. It increases GI motility.
Q: Does serotonin produce flushing?
A: No. This is because of bradykinin.
Q: What is responsible for valvular lesions?
A: Serotonin via HT-2B. Serotonin activates FGF, which increases fibrogenesis in the valves.
Q: What are the symptoms of histamine excess?
A: Histamine produces atypical flushing.
Q: What are the symptoms of kallikrein and its product bradykinin?
A: They produce vasodilation and the typical flush that is seen
**Clinical features **
- #Pearl The classical carcinoid syndrome is mainly seen in midgut carcinoid with liver mets.
Q. Describe the typical flush in carcinoid syndrome.
- Occurs suddenly
- Lasts for 30 s to 30 min
- Severe cases associated with reduced BP and increased HR
- Pink to violet in colour
- Involves the face, neck, upper chest
- Mild burning sensation
Q. Describe other endocrine causes of Flushing.
- MTC
- Pheochromocytoma
- Menopause
- VIPoma
- Niacin use
- Alcohol use
- Nitrate use
- Systemic mastocytosis
Q. Do they occurs spotenously or are they provoked?
- Can be spontaneous or provoked
- Provoked by anesthesia, carcinoid crisis in severe cases, alcohol, emotional distress, etc.
Q. What are 5 E's with which carcinoid symptoms are exacerbated?
- Exercise
- Emotion
- Ethanol
- Epinephrine
- Eating
**Variant syndromes **
Q: What is a feature of gastric carcinoid syndrome?
A: They have atypical flush without diarrhea. It is because of histamine. Flush is pruritic, patchy, sharply demarcated.
Q: What about bronchial carcinoid variant?
A: Flush is more severe here and lasts longer. May be associated with periorbital edema, hypotension, etc. Also due to histamine probably.
Q: Are flushes in Carcinoid dry or wet?
A: Carcinoid flushes are typical dry, unlike other causes of flushes like menopausal flushing. Dry means not associated with excessive sweating.
Q: How to distinguish diarrhea of Carcinoid from IBS diarrhea?
A: Carcinoid diarrhea can be nocturnal and can awaken patient from sleep. IBS diarrhea occurs during daytime only and not during sleep. Also remember diarrhea in Carcinoid syndrome is secretory diarrhea which persists while fasting, while in IBS it occurs after meal and not with fasting