The secretion of G-17 from the G-cells in the antrum mucosa is a result of a stimulation by various factors e.g. of dietary protein stimulus. High acidity in the stomach inhibits the secretion of Gastrin-17. In a normal stomach, protein stimulation or the lack of acid will result in an increase in the plasma Gastrin-17 level. In advanced or severe atrophic gastritis of the antrum, the fasting (basal) level of Gastrin-17 in plasma is low and no increase will occur following protein stimulation. The magnitude of the decline of the Gastrin-17 concentration and its response to stimulus depends on the degree of atrophy: the more severe the atrophy, the lower the concentration of Gastrin-17, and the weaker the Gastrin-17 response to stimulus.