what exactly is Swiss Chems MK677 Ibutamoren? MK-677, also referred to as ibutamoren or ibutamoren mesylate, is usually a peptide that belongs to the growth hormone secretagogues group (GHSR). It works by mimicking the motion of your hunger hormone ghrelin. It binds to at least one of the growth hormone secretagogue receptors (GHSR) within the brai