Which of the following symptoms are present in carcinoid syndrome?

Carcinoid syndrome occurs due to the secretion of serotonin and other vasoactive substances from neuroendocrine tumors, most commonly arising from the gastrointestinal tract, particularly the ileum.

Flushing of the skin is a hallmark symptom of carcinoid syndrome. This flushing is typically triggered by certain foods, stress, or alcohol and is caused by the vasodilatory effects of serotonin and other substances released by the tumor.

Diarrhea is another prominent symptom associated with carcinoid syndrome. High levels of serotonin can lead to increased intestinal motility and secretory diarrhea as serotonin acts on the gut to enhance peristalsis.

Additionally, the presence of valvular lesions, particularly right-sided heart lesions, is often observed in patients with carcinoid syndrome. This phenomenon occurs because serotonin is metabolized in the lungs; however, when a carcinoid tumor secretes excessive serotonin into the bloodstream, it can lead to fibrosis of the heart valves, resulting in tricuspid regurgitation and pulmonary stenosis.

Since flushing, diarrhea, and valvular lesions are all characteristic manifestations of carcinoid syndrome, the correct response encompasses all of these symptoms as they collectively define the clinical picture of carcinoid syndrome.