Stimulates the secretion of gonadotropins. Expressed in the cell bodies of a cluster of neurons in the preoptic region. Teleost species possess three paralogous GnRHs: mdGnRH and cGnRH-II have been identified in tetrapods; sGnRH has no tetrapod ortholog and is thought to be a duplication of cGnRH-II. Belongs to the GnRH family.