Which two substances are released in carcinoid syndrome related to its effects?

In carcinoid syndrome, the key substances released that contribute to its effects are histamine and serotonin. These are produced by neuroendocrine tumors, often found in the gastrointestinal tract, that secrete these compounds into the bloodstream.

Histamine plays a role in various physiological processes, including vasodilation and increased vascular permeability, which can lead to flushing and other symptoms commonly associated with carcinoid syndrome. It contributes to the characteristic symptoms of flushing, diarrhea, and bronchoconstriction seen in these patients.

Serotonin is another critical substance in carcinoid syndrome. It is involved in the regulation of mood, appetite, and digestion, but in this syndrome, excess serotonin is converted into a metabolite called 5-hydroxyindoleacetic acid (5-HIAA), which can be measured in urine to help in the diagnosis. The overproduction of serotonin leads to gastrointestinal symptoms, such as diarrhea and even heart issues, specifically tricuspid valve disease and pulmonary valve stenosis due to its systemic effects.

The other substances listed, such as parathyroid hormone and choline acetyltransferase, are not typically associated with the pathophysiology of carcinoid syndrome. Parathyroid hormone is related to calcium regulation