[Growth hormone and prolactin receptors belong to a new receptor family. Biological and medical aspects].

The molecular structures of the receptors of growth hormone and prolactin have recently been identified by molecular cloning, and have been characterized in a number of species and different tissues. The receptors consist of one polypeptide chain with a single transmembrane region. The extracellular region contains cysteines for disulphide bonding and potential sites for glycosylations. The intracellular part which mediates the biological actions displays considerable heterogeneity of size. A high degree of homology is demonstrated between the extracellular part of these receptors and the receptors of a number of cytokines, interferons and growth factors. Together they comprise a new family of receptors called the cytokine/growth hormone/prolactinreceptor family. Their structure is reviewed, along with the actions of growth hormone and prolactin in vivo. In spite of numerous biological effects the molecular mechanisms of actions for this class of receptors are unknown, even though they convey important cell regulatory functions. The molecular analysis of growth hormone receptor has provided new medical insight on the results of growth hormone replacement therapy in persons with deficient growth.