Trefoil factor 1 belongs to the trefoil factor family that consists of three members named TFF1, TFF2 and TFF3. They are characterized by having at least one copy of the trefoil motif, a 40-amino acid domain that contains three conserved disulfides. Mature human TFF1 shares 67% amino acid sequence identity with mouse and rat TFF1. The TFFs are stable secretory proteins expressed highly in the gastrointestinal tract (gastric mucosa). TFF1 is an essential protein for normal differentiation of the antral and pyloric gastric mucosa and functions as a stabilizer of the mucous gel overlying the gastrointestinal mucosa that provides a physical barrier against various noxious agents. TFF1 is down-regulated during the progression from gastritis to gastric dysplasia to gastric cancer, although it is up-regulated in breast and prostate cancers. TFF1 inhibits the formation of calcium oxalate crystals, and its excretion in the urine is reduced in patients with kidney stones.