MK-677, also known as Ibutamoren, is a growth hormone secretagogue originally developed by Reverse Pharmacology. A secretagogue is a substance that stimulates the secretion of another substance—in this case, MK-677 signals the pituitary gland to release growth hormone. MK-677 is often compared to secretagogue peptides like GHRP-6 or Ipamorelin, but unlike these, it doesn’t require injections. Originally developed to treat elderly patients suffering from muscle wasting, obesity, and osteoporosis, MK-677 is often sold and referred to as a Selective Androgen Receptor Modulator (SARM), although it is not actually a SARM and is non-hormonal. As such, MK-677 does not affect natural testosterone production or the Hypothalamus-Pituitary-Testes-Axis (HPTA). This means no post-cycle therapy (PCT) is necessary, and MK-677 can be safely used during PCT or as a bridge between steroid cycles.
MK-677 works through four main mechanisms:
Increasing Growth Hormone Releasing Hormone (GHRH).
Amplifying GHRH signalling in somatotrophs of the anterior pituitary gland.
Reducing somatostatin release (somatostatin inhibits growth hormone release).
Inhibiting somatostatin receptor signalling.
