All ofthe following are true about Zollinger-Ellsioii syndrome, except-

Pathophysiology The tumour secretes gastrin, which stimulates acid secretion to its maximal capacity and increases the parietal cell mass three- to sixfold. The acid output may be so great that it reaches the upper small intestine, reducing the luminal pH to 2 or less. Pancreatic lipase is inactivated and bile acids are precipitated. Diarrhoea and steatorrhoea result. Around 90% of tumours occur in the pancreatic head or proximal duodenal wall. At least half are multiple and tumour size can vary from 1 mm to 20 cm. Approximately one-half to two-thirds are malignant but are often slow-growing. Between 20% and 60% of patients have multiple endocrine neoplasia (MEN) type 1 (p. 688). Clinical features The presentation is with severe and often multiple peptic ulcers in unusual sites, such as the post-bulbar duodenum, jejunum or oesophagus. There is a poor response to standard ulcer therapy. The history is usually sho, and bleeding and perforations are common. Diarrhoea is seen in one-third or more of patients and can be the presenting feature. Investigations Hypersecretion of acid under basal conditions, with little increase following pentagastrin, may be confirmed by gastric aspiration. Serum gastrin levels are grossly elevated (10- to 1000-fold). Injection of the hormone secretin normally causes no change or a slight decrease in circulating gastrin concentrations, but in Zollinger-Ellison syndrome it produces a paradoxical and dramatic increase in gastrin. Tumour localisation (and staging) is best achieved by a combination of CT and EUS; radio-labelled somatostatin receptor scintigraphy and 68gallium DOTATATE PET scanning may also be used for tumour detection and staging. Ref Davidson edition23rd pg802