All of the following statements about carcinoid syndrome are true except
**Core Concept**
Carcinoid syndrome is a collection of symptoms caused by the release of vasoactive substances, primarily serotonin (5-HT), from a carcinoid tumor. This syndrome occurs when the tumor metastasizes to the liver, which normally inactivates these substances, but in this case, allows them to enter the systemic circulation.
**Why the Correct Answer is Right**
The classic symptoms of carcinoid syndrome include flushing, diarrhea, wheezing, and heart valve abnormalities. These symptoms arise due to the vasoactive effects of serotonin and other substances released by the tumor. The flushing is thought to be due to the vasodilatory effects of serotonin, while the diarrhea is caused by the stimulation of intestinal secretions. The wheezing is a result of bronchoconstriction, and the heart valve abnormalities are due to the fibrotic effects of serotonin on the valves.
**Why Each Wrong Option is Incorrect**
**Option A:** This statement is incorrect because carcinoid tumors typically arise from the argentaffin cells of the small intestine, not the stomach.
**Option B:** This statement is incorrect because the symptoms of carcinoid syndrome can be exacerbated by certain foods, such as tyramine-rich foods, which can increase serotonin levels.
**Option C:** This statement is incorrect because octreotide, a somatostatin analog, is actually used to treat carcinoid syndrome by reducing the secretion of vasoactive substances.
**Clinical Pearl / High-Yield Fact**
The flush associated with carcinoid syndrome can be exacerbated by stress, temperature changes, and certain foods, making it a useful diagnostic clue.
**Correct Answer: D. Octreotide is used to treat carcinoid syndrome by increasing the secretion of vasoactive substances.**