Parathyroid hormone-related peptide (PTHrP), originally isolated as a responsible factor for humoral hypercalcemia of malignancy, has been demonstrated to overexpress even in non-hypercalcemic gastrointestinal malignancies. PTHrP and its receptor mRNA expression has been detected in a variety of normal tissues in neonate and adults. PTHrP might be involved in growth and differentiation on fetal gut epithelium, and an important gastrointestinal peptide which regulates gastrointestinal contractile activity in a paracrine/autocrine fashion. Exogenous PTHrP shows a relaxant effect on gastrointestinal muscle strips through PTH/PTHrP receptor in vitro. Increase PTHrP mRNA was induced by distention and contraction in the smooth muscle of the stomach, and stress-induced abnormal contractions was deeply related to PTHrP suppression by steroid.