KiSS-1 gene encodes metastin, also known as kisspeptin or KiSS-1 peptide, which binds to a G protein-coupled receptor GPR54. KiSS-1 is dominantly expressed in brain (e.g. anteroventral periventricular nucleus, AVPV arcuate nucleus, ARC), placenta, and pancreas, etc. Metastin plays an important role in regulating the GnRH secretion in brain and MMP-9 expression in placenta, which is associated with development of puberty and sex maturation (e.g. Idiopathic hypogonadotropic hypogonadism, IHH) as well as placentation (e.g. pre-eclampsia), respectively. Metastin was originally discovered as a tumor metastasis suppressor (e.g. melanoma, breast cancer).