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 team (GHSR). It works by mimicking the action of the starvation hormone ghrelin. It binds to one of the growth hormone secretagogue receptors (GHSR) from the brain, suppor