Gastritis and peptic ulcer disease involve damage to the lining of the stomach or duodenum (the first segment of the small intestine). These disorders are usually caused by
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Stomach acid (hydrochloric acid)
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Digestive enzymes (especially pepsin)
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Use of certain drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs)
In Zollinger-Ellison syndrome, a rare tumor that usually occurs in the duodenum, pancreas, or adjacent structures, produces a hormone called gastrin that causes the stomach to produce too much acid.
Usually the lining of the stomach is protected by certain defense mechanisms. The cells that line the stomach secrete mucus and bicarbonate. The mucus coats the inside of the stomach to protect it from being damaged by acid and digestive enzymes. The bicarbonate within and under the mucus helps neutralize stomach acid. When these defense mechanisms are disrupted, for example, by the bacterium Helicobacter pylori or aspirin, people may develop gastritis or peptic ulcer disease. There are many treatment options available (see Drug Treatment of Stomach Acid).
