Zollinger-Ellison (Z-E) syndrome is characterized by great (e.g., 20-fold) elevation of:

Zollinger-Ellison syndrome is characterized by excessively high levels of gastrin in the bloodstream. This condition typically arises due to gastrin-secreting tumors known as gastrinomas, which are often found in the pancreas or the duodenum. The elevated gastrin levels lead to increased gastric acid secretion, resulting in severe recurrent peptic ulcers and gastrointestinal symptoms. This significant (often 20-fold or more) elevation of gastrin is the hallmark of the syndrome and is essential for diagnosing the condition.

The other substances listed also play roles in digestion but are not specifically associated with the hallmark characteristics of Zollinger-Ellison syndrome. For instance, cholecystokinin is involved in stimulating gallbladder contraction and promoting digestion of fat and protein but does not exhibit the extreme elevation seen in gastrin during Z-E syndrome. Pepsin is a digestive enzyme that breaks down proteins in the stomach but is not a regulatory hormone. Glucagon, primarily involved in glucose metabolism, does not show the significant increase characteristic of this syndrome. The focus on gastrin is crucial for understanding the underlying pathophysiology of Zollinger-Ellison syndrome.