What MK677 is, in plain English.
MK677 is a non-peptide small molecule that acts as an agonist at the ghrelin receptor, the same receptor Ipamorelin works through. Its molecular formula is C27H36N4O5S, with a molecular weight of about 528.7 g/mol and the CAS number 159634-47-6, and it has been studied under the research name Ibutamoren. Where Ipamorelin is a peptide, MK677 was developed in the 1990s as an orally active compound: a molecule built to copy the action of the growth-hormone-releasing peptides while surviving digestion. That oral activity, together with a long duration of action (IGF-1 levels in people are reported to stay raised for up to 24 hours after a single oral amount), is what distinguishes it in the growth-hormone-secretagogue literature, where it remains one of the most-cited compounds. It is commonly researched in growth-hormone-axis and body-composition models, and in sleep research, where changes in REM and slow-wave sleep have been reported. Unlike most compounds in the range it has a sizeable human literature: it has been investigated in children and older adults with growth-hormone deficiency, and human studies have measured its effect on muscle mass and bone mineral density. Even so it has not been approved as a medicine, and the World Anti-Doping Agency lists it by name, as ibutamoren (MK-677), among the prohibited growth-hormone secretagogues. Supplied as 60 capsules of 10mg per pack; not a peptide, so no reconstitution.
