Relaxin-2, also called H2 relaxin, is a peptide hormone that plays an important role in female reproduction. It circulates in the blood as a disulfide-linked dimer of alpha and beta chains. Relaxin is best known as a hormone of parturition that promotes growth and softening of the cervix, development of the mammary gland, and has a marked impact on the uterus. In particular, it promotes angiogenesis, inhibits MMP production and activity, and downregulates estrogen receptor-alpha expression. Relaxin-2 confers its activity by binding to leucine-rich guanine nucleotide-binding (G-protein) coupled receptors, LGR7 and LGR8.