MK-677 (Ibutamoren)

MK-677 is not a peptide — it is a small, orally bioavailable, non-peptidyl compound. It is included here alongside GH secretagogues because it works through the same receptor as ghrelin-mimetic peptides: it binds the ghrelin receptor (GHS-R1a) on pituitary somatotrophs and hypothalamic neurons, stimulating pulsatile release of endogenous growth hormone and, secondarily, raising IGF-1. Because it is a small molecule (not a chain of amino acids degraded by gut proteases), it survives oral dosing, unlike true peptide GH secretagogues that require injection.

MK-677 has more human randomized-controlled-trial data than most compounds sold in the same research-chemical market, but none of it has translated into an approved drug. A placebo-controlled 8-week trial in obese men (Svensson et al., 1998) found daily oral MK-677 increased GH pulsatility, IGF-1, and fat-free mass. A two-year randomized, placebo-controlled trial in healthy older adults (Nass et al., 2008, n=65) found sustained increases in fat-free mass and restoration of GH/IGF-1 toward more youthful levels, but no significant improvement in physical function or strength — the study's clinically relevant endpoints — and it raised fasting glucose and reduced insulin sensitivity. Trials in other populations (hip-fracture recovery, sarcopenia) have similarly shown body-composition signals without consistent functional benefit, and development for elderly frailty and pediatric growth hormone deficiency did not lead to regulatory approval.

Educational overview only — no dosing instructions in the public hub.

In controlled trials, the most consistent adverse effects were increased appetite, mild-to-moderate lower-extremity/soft-tissue edema, muscle and joint aches, transient numbness/paresthesia (carpal-tunnel-like symptoms from fluid retention), and increases in fasting blood glucose with reduced insulin sensitivity — a signal relevant to anyone with pre-diabetes or diabetes risk. Because it chronically elevates GH/IGF-1, it carries the same theoretical class concerns as other GH secretagogues regarding tissue growth and should not be used with active or suspected malignancy. Long-term cardiovascular and cancer-risk outcomes beyond about two years have not been studied.

MK-677 sold outside licensed pharmaceutical channels is an unregulated research chemical. Independent third-party CoA — identity and purity by HPLC, quantification, and mass-spectrometry confirmation — is the minimum standard; a manufacturer's own certificate is not a substitute, and lot numbers on the CoA should be checked against the vial/product in hand.

Not approved by the FDA, EMA, or MHRA for any indication; clinical development (including for elderly frailty and pediatric growth hormone deficiency) did not result in marketing authorization anywhere. It is commonly sold as a research chemical/RUO (research use only) product, not as a medicine, and is not legal to market for human consumption in the US, EU, or UK. Regulatory and anti-doping status (it is prohibited by WADA as a growth hormone secretagogue) should be checked independently as rules vary and change.