Kisspeptin (a.k.a. metastin) is a naturally occurring protein in humans that plays important roles in hormone signaling during puberty and reproduction. It is also thought to alter mood and behavior, promote angiogenesis, and regulate kidney function. The peptide has also been found in the brain and is known to suppress tumor growth and metastasis (spread). The peptide is of greatest scientific interest for its ability to influence gonadotropin releasing hormone (GnRH).