Parathyroid Hormone-Related protein signals through its receptor PTHR1, regulating endochondral bone development and epithelial-mesenchymal interactions. PTHRP is an anti-proliferative factor that regulates epidermal cell growth. Because of its structural homology with PTH and binding to the PTH/PTHRP receptor, PTHRP can mimic the action of PTH, but has evolved to regulate local tissue functions, in contrast to the systemic function of parathyroid hormone. To carry out its diverse biologic roles, PTHRP functions as a poly-hormone that gives rise to several biologically active peptides, each of which presumably has its own receptor. To broaden its repertoire even further, it appears to have intracrine effects in the nucleus of cells that produce it, in addition to having autocrine, juxtacrine, paracrine, and possibly endocrine effects after secretion. (from OMIM 168470 and NCI)