The eCG molecule
eCG (equine chorionic gonadotropin) is a glycoprotein hormone with gonad-stimulating activity.
Other gonadotropins include FSH (follicle-stimulating hormone) and LH (luteinizing hormone). They are produced by the pituitary, while eCG is produced by the placenta.
FSH and LH act in synergy to stimulate ovulation and follicular growth, making them essential for fertility and reproduction.
eCG is structurally similar to eLH (equine LH) and thereby acts as an agonist for the LH receptor in horses.
eCG and eLH are mainly distinguished by glycosylation, as eCG is the most extensively glycosylated of all known glycoprotein hormones in mammals.
This extensive glycosylation makes eCG very stable, with a long half-life in blood.
When injected to almost all other mammals, eCG not only binds to the LH receptor, but also to the FSH receptor, giving it the unique ability to mediate both FSH- and LH-like activity in other animals.
The reason behind this double functionality is unknown, although eCG’s extensive glycosylation likely plays a role.
The double FSH- and LH-like functionality and high stability of eCG makes it very desirable for use in reproductive veterinary medicine.