A 28-year-old man is evaluated for recurrent peptic ulcer disease, apparently refractory to pharmacologic intervention. Serum gastrin is markedly elevated. These findings are most characteristic of which of the following?

- Recurrent intractable peptic ulcer disease is suggestive of Zollinger-Ellison syndrome characterized by excess gastrin production, most often from a gastrinoma. - Cushing syndrome results from excess of coisol caused d/t adrenal/ pituitary adenoma. - Glucagonoma is rare neuroendocrine tumor of pancreatic alpha cells, that can cause hyperglycemia. - Whipple triad (episodic hyperinsulinemia + hypoglycemia causing CNS dysfunction, reversible by glucose administration) is seen with insulinoma.