A 45-year-old woman complains of right upper quadrant abdominal pain, weight loss, dry mouth, increased urine production, and foul-smelling fatty stools. She has a recent history of mild diabetes mellitus. Abdominal ultrasound examination reveals gallstones and a solitary 1.5-cm mass in the pancreas. Which of the following hormones would most likely be elevated in the blood of this patient?

Delta cell tumors (somatostatinomas) produce a syndrome consisting of mild diabetes mellitus, gallstones, steatorrhea, and hypochlorhydria. These effects result from the inhibitory action of somatostatin on the secretion of hormones by cells of the endocrine pancreas, acinar cells of the pancreas, and certain hormone-secreting cells in the gastrointestinal tract. Somatostatin also inhibits the pituitary release of growth hormone. None of the other choices are associated with mild diabetes or cholelithiasis.Diagnosis: Somatostatinoma, cholelithiasis