The expanding growth hormone/prolactin family

Introduction A new member of the growth hormone (GH)/prolactin family was characterized in 1984 (Linzer & Nathans, 1984), and named proliferin in recognition of its production by proliferating mouse fibroblasts. Since then there has been a remarkable proliferation of new GH- and prolactin-like proteins in what had seemed to be an old and stable family. Many of these proteins are produced in the placenta, which is now also recognized as a major source of proliferin itself, but a new pituitary hormone has been identified in fish, and possible homology of GH and prolactin with other cytokines is also now apparent. The purpose of this communication is to summarize current knowledge of the new proteins in this family and to assess their relationships to GH and prolactin. The GH gene family in humans In humans, the gene for GH (hGH-N) occurs as a member of a cluster of five related genes