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?

**Core Concept**
The patient's symptoms and abdominal ultrasound findings suggest a diagnosis of a pancreatic tumor, likely a glucagonoma, which is a rare neuroendocrine tumor that secretes glucagon. Glucagon is a hormone produced by the pancreas that raises blood glucose levels by stimulating glycogenolysis and gluconeogenesis.

**Why the Correct Answer is Right**
Glucagonoma is characterized by the excessive production of glucagon, leading to symptoms such as weight loss, dry mouth, increased urine production, and abdominal pain. The presence of gallstones and a solitary mass in the pancreas supports the diagnosis of a pancreatic tumor. The recent history of mild diabetes mellitus may be related to the glucagonoma's effect on glucose metabolism. The foul-smelling fatty stools are a classic symptom of steatorrhea, which occurs due to the impaired release of pancreatic enzymes.

**Why Each Wrong Option is Incorrect**
**Option A:** Insulin would be decreased in the blood of this patient, as the glucagonoma would lead to increased glucose levels, making insulin production less necessary.
**Option B:** Gastrin is a hormone produced by G cells in the stomach and is involved in the secretion of gastric acid. Elevated gastrin levels are associated with Zollinger-Ellison syndrome, which presents differently than glucagonoma.
**Option C:** Somatostatin is a hormone produced by D cells in the pancreas and inhibits the release of other hormones, including glucagon. Elevated somatostatin levels would not explain the patient's symptoms.
**Option D:** Vasoactive intestinal polypeptide (VIP) is a hormone produced by the pancreas and is involved in the regulation of smooth muscle contraction and secretion. Elevated VIP levels are associated with VIPoma, which presents with different symptoms than glucagonoma.

**Clinical Pearl / High-Yield Fact**
Glucagonoma is a rare pancreatic tumor that can be associated with a characteristic rash known as necrolytic migratory erythema (NME), which is often preceded by the patient's symptoms. NME is a distinctive skin rash that can aid in the diagnosis of glucagonoma.

**Correct Answer: C. Glucagon**

✓ Correct Answer: D. Somatostatin