* Secretin stimulation test, which measures evoked gastrin levels
* Fasting gastrin levels, on at least three separate occasions
* Gastric acid secretion and pH
Proton pump inhibitors (such as omeprazole and lansoprazole) and histamine H2-receptor antagonists (such as famotidine and ranitidine) are used to slow down acid secretion. Cure is only possible if the tumors are surgically removed, or treated with chemotherapy.