Ibutamoren or MK-677 is a popular SARM or Selective Androgen Receptor Modulator which is also known as MK-0677, L-163 and 191, it also had former tentative brand names like Nutrabol, Oratrope and Ibutamoren Mesylate. It is a long acting, non-peptide, potent and selective agonist of ghrelin receptor which is a growth hormone secretagogue that mimics the effects of a growth hormone.