What is Swiss Chems MK677 Ibutamoren? MK-677, often called ibutamoren or ibutamoren mesylate, is actually a peptide that belongs to The expansion hormone secretagogues group (GHSR). it really works by mimicking the motion on the starvation hormone ghrelin. It binds to one of The expansion hormone secretagogue receptors (GHSR) in the Mind, helping r