A 40-year-old woman with a history of hyperparathyroidism presents with a 2-month history of burning epigastric pain. The pain can be relieved with antacids or food. The patient also repos a recent history of tarry stools. She denies taking aspirin or NSAIDs. Laboratory studies show a microcytic, hypochromic anemia . Gastroscopy reveals a bleeding mucosal defect in the antrum. Which of the following best characterizes the pathogenesis of epigastric pain in this patient?