American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What does a fasting serum gastrin level greater than 1000 pg/mL indicate in the context of Zollinger-Ellison syndrome (ZES)?

1. Normal gastric function

2. Possible gastrinoma

3. Chronic pancreatitis

4. Peptic ulcer disease

The correct answer is: Possible gastrinoma

A fasting serum gastrin level greater than 1000 pg/mL is a significant indicator in the diagnosis of Zollinger-Ellison syndrome (ZES). ZES is characterized by gastrin-secreting tumors, known as gastrinomas, which lead to excessive gastric acid secretion and can cause recurrent peptic ulcers. When serum gastrin levels exceed 1000 pg/mL while fasting, it strongly suggests the presence of a gastrinoma. This threshold is used clinically to differentiate between normal physiological conditions and pathological states such as ZES. In normal individuals, fasting serum gastrin levels are generally much lower. Elevated levels can also occur due to other conditions, but the magnitude of elevation (over 1000 pg/mL) is particularly predictive of a gastrinoma rather than reflecting normal gastric function, chronic pancreatitis, or peptic ulcer disease alone. Thus, in the context of ZES, this criterion becomes a key diagnostic tool in identifying gastrin-secreting tumors.