Fig. 1

Luteinizing hormone (LH) and human chorionic gonadotropin (hCG) have similar structural features. LH (left panel) is a glycoprotein consisting of two subunits, the α subunit and the β subunit (blue). The α subunit is similar to that of follicle-stimulating hormone (FSH) and hCG, with two carbohydrate attachment sites. On the other hand, the β subunit has only one carbohydrate attachment site. The Though structurally similar to LH, hCG (right panel) has a notable difference: it contains a long carboxy-terminal segment that is O-glycosylated (O-linked CHO), which gives hCG a longer half-life. In the illustration, the α and β subunits are represented by red and blue strands, respectively, with light blue balls representing the carbohydrate chains. Adapted from Leão Rde B, Esteves SC. Gonadotropin therapy in assisted reproduction: an evolutionary perspective from biologics to biotech. Clinics (Sao Paulo). 2014;69(4):279–93. This article is distributed under the Creative Commons Attribution License (CC BY 4.0)