Growth Hormone/Prolactin Family

Growth hormone (GH), prolactin (PRL), somatolactin (SL), and a mammalian placental hormone, placental lactogen (PL), form a family that share a common tertiary structure. They produce their biological effects by interacting with single transmembrane-domain receptors that belong to the class 1 cytokine receptor family. The binding of these hormones to their receptors causes receptor dimerization, and activates Janus kinase 2 (JAK2), a tyrosine kinase that initiates the JAK-STAT (signal transducers and activators of transcription) pathway. The principal biological role of GH, the control of postnatal growth, has remained quite consistent throughout vertebrate evolution and is largely mediated by insulin-like growth factors (IGFs). PRL has many and diverse roles, including control of water and salt balance. SL has a wide range of biological activities, including body-color regulation. PL modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus.