Which of the following is NOT a possible symptom of carcinoid syndrome?

Carcinoid syndrome is a collection of symptoms that may occur in patients with carcinoid tumors, which are neuroendocrine tumors that can secrete various substances such as serotonin. The hallmark symptoms of carcinoid syndrome include diarrhea, flushing, and palpitations, all of which are directly associated with the excessive release of serotonin into the bloodstream.

Diarrhea is particularly common, as high levels of serotonin can stimulate intestinal motility, leading to watery and frequent stools. Palpitations can result from the effects of serotonin on the heart and blood vessels, leading to vasodilation and tachycardia.

Weight fluctuations may also occur in patients with carcinoid syndrome due to changes in diet (from symptoms like diarrhea), metabolic alterations, or the effects of the tumor itself. However, vision changes are not typically associated with carcinoid syndrome. While other health conditions can indeed cause vision problems, changes in vision are not recognized as a symptom of carcinoid syndrome specifically. Thus, the correct answer identifies an option that does not align with the established symptoms of this condition.