Chemistry of human choriogonadotropin

Human choriogonadotropin is the placental member of the homologous glycoprotein hormone family which includes the pituitary hormones lutropin, follitropin and thyrotropin all of which share a common alpha subunit but different target-specific beta subunits. HCG differs chemically from the pituitary hormones by its higher carbohydrate content, high sialic acid content, lack of sulfation, longer plasma half-Life and capability to survive passage through the kidney essentially intact. Since crystallographic models are not available, hormone topography has been explored by immunochemical methods using both polyclonal and monoclonal antibodies. Studies of the immunochemistry of the beta COOH-terminal region have shown that determinants dependant upon carbohydrate content exist within this region. Such work also led to development of extremely sensitive and specific immunoassays for measurement of the hormone.