GIT Hormones

A 60-year-old man with type 2 diabetes is found to have postprandial hyperglycemia. An oral glucose tolerance test shows higher insulin secretion compared to an intravenous glucose load. Which hormone explains the higher insulin response to oral glucose?

• GIP

• CCK

• VIP

• Gastrin

Answer explanation

Gastric inhibitory peptide (GIP) is also called glucose-dependent insulinotropic peptide. It enhances insulin secretion when glucose is taken orally, known as the incretin effect, which is absent in intravenous glucose administration.

A 50-year-old woman presents with profuse watery diarrhea, muscle weakness, and severe dehydration. Blood tests reveal hypokalemia and achlorhydria. Which hormone-secreting tumor is most consistent with her presentation?

• Gastrinoma

• VIPoma

• Insulinoma

• Glucagonoma

Answer explanation

VIPoma, a rare neuroendocrine tumor, causes WDHA syndrome: Watery Diarrhea, Hypokalemia, and Achlorhydria. VIP stimulates intestinal electrolyte and water secretion, leading to profuse diarrhea and metabolic disturbances.

A 70-year-old diabetic patient on insulin therapy has episodes of severe nausea and delayed gastric emptying. A new pancreatic co-secreted peptide is suspected to contribute to this effect. Which hormone is responsible for slowing gastric emptying and increasing satiety in this context?

• VIP

• PYY

• Amylin

• Motilin

Answer explanation

Amylin, co-secreted with insulin from pancreatic β-cells, delays gastric emptying and promotes satiety. In diabetics, excess or exogenous amylin can contribute to nausea and gastroparesis symptoms.

A 45-year-old woman complains of postprandial bloating and early satiety. She recently started a high-fat diet. Investigations show delayed gastric emptying. Which hormone is most likely contributing to her symptoms by slowing gastric emptying and promoting satiety?

• Motilin

• PYY

• Gastrin

• Secretin

Answer explanation

PYY is released by L cells in the ileum and colon in response to a meal, especially rich in fats. It decreases appetite, reduces gastric motility, and slows gastric emptying, contributing to early satiety and bloating.

A 55-year-old man presents with recurrent epigastric pain, chronic diarrhea, and multiple peptic ulcers in unusual locations (e.g., jejunum). Laboratory tests reveal markedly elevated fasting serum XX levels. Which hormone XX is most likely responsible for his symptoms?

• Secretin

• Cholecystokinin

• Somatostatin

• Gastrin

Answer explanation

The constellation of refractory peptic ulcers, diarrhea, and high serum gastrin levels suggests Zollinger-Ellison syndrome (gastrinoma). Gastrin stimulates parietal cells to secrete excess HCl, leading to ulcer formation in unusual locations and diarrhea from acid-induced mucosal injury.

A 68-year-old man has long-standing dyspepsia and undergoes an upper GI endoscopy, which reveals gastric mucosal atrophy. He also reports fatigue and glossitis. Lab tests show megaloblastic anemia and low vitamin B12 levels. The loss of which gastric secretion is most likely contributing to his anemia?

• Gastrin

• Intrinsic factor

• Somatostatin

• Secretin

Answer explanation

Intrinsic factor, secreted by parietal cells, is essential for vitamin B12 absorption in the terminal ileum. Atrophic gastritis leads to decreased intrinsic factor, resulting in vitamin B12 deficiency and megaloblastic anemia.