Decreased pepsinogen is mainly due to diseases such as chronic superficial gastritis, chronic atrophic gastritis, erosive gastritis, and gastric cancer. Pepsinogen 1 and pepsinogen 2 are secreted by the principal cells of the fundic glands and the mucus neck cells in the gastric mucosa. The mucus neck cells of the cardia and pylorus glands and the duodenum can also secrete pepsinogen 2. Inflammation of the gastric mucosa can lead to a mild decrease in both pepsinogens. In atrophic gastritis or atypical hyperplasia of the gastric mucosal cells, pepsinogen 1 is significantly decreased and pepsinogen 2 is mildly increased. It may be related to the decrease of gastric acid secretion and the decrease of pepsin consumption. When there is gastric cancer, atrophy and atypical hyperplasia of the gastric mucosa due to the invasion of tumor cells will lead to the decrease of both secretion.