CSH1

CSH1 is a human gene that encodes chorionic somatomammotropin-1 (CSH-1), also known as placental lactogen-1. It is a member of the growth hormone/prolactin family of hormones, produced by the placenta during pregnancy.

Location and family: CSH1 lies within the placental hormone gene cluster on chromosome 17 in humans, alongside the related gene CSH2. In humans, CSH1 and CSH2 are the primary placental lactogen genes, contributing to the repertoire of hormones secreted by the placenta.

Expression and product: CSH1 is expressed in placental trophoblasts, especially the syncytiotrophoblast layer, and the protein is secreted into the maternal circulation as pregnancy progresses.

Function: Placental lactogens, including CSH-1, have lactogenic and growth-promoting activities akin to prolactin and growth hormone. They signal through prolactin and growth hormone receptors to influence maternal metabolism, promoting nutrient availability for the fetus, enhancing lipolysis, and modulating insulin sensitivity. They also contribute to mammary gland development in preparation for lactation.

Clinical notes: Levels of placental lactogens reflect placental function and fetal well-being in pregnancy, and alterations can be observed in certain placental disorders or pregnancy complications. While not a routine diagnostic test, CSH1 expression and placental lactogen levels are studied in obstetric research as indicators of placental health.

Evolution and nomenclature: CSH1 is part of a small gene family that expanded by duplication in mammals. CSH2 is a closely related paralog. The placental lactogen system shows species-specific variation across mammals.