Which of the following is a classic feature of Zollinger-Ellison syndrome?

In Zollinger-Ellison syndrome, a classic feature is chronic diarrhea. This condition is characterized by gastrin-secreting tumors, typically called gastrinomas, which lead to excessive gastric acid production. The high levels of acid can cause severe gastrointestinal symptoms, including chronic diarrhea, as the excess acid irritates the gastrointestinal lining and disrupts normal digestive processes.

The diarrhea associated with Zollinger-Ellison syndrome is often a result of both increased gastric acid secretion and the resulting malabsorption of nutrients, contributing to the clinical symptoms. Patients may experience steatorrhea (fatty stools) due to the inability to properly digest fats in the presence of excessive gastric acid.

In contrast, the other options do not align with the typical clinical presentations of this syndrome. Increased insulin sensitivity and hypoglycemia are more associated with insulinomas or diabetes mellitus, while frequent epistaxis is not a recognized symptom of Zollinger-Ellison syndrome. Therefore, chronic diarrhea emerges as the most definitive and classic feature of this condition.