Overview
MK-677 (Ibutamoren) is a non-peptide, orally active ghrelin mimetic and growth hormone secretagogue. Unlike injectable GHRPs, it is taken by mouth and stimulates sustained increases in GH and IGF-1. Popular among athletes and biohackers for muscle mass, fat loss, sleep quality, and anti-aging applications.
Mechanism of action
MK-677 selectively binds to and activates the ghrelin receptor (GHSR-1a) in the pituitary and hypothalamus, mimicking the action of the endogenous hunger hormone ghrelin. This activation triggers pulsatile growth hormone release from the anterior pituitary and downstream elevation of IGF-1 from the liver. Unlike exogenous GH, MK-677 preserves the natural pulsatile GH pattern. It also suppresses somatostatin signaling, which further amplifies GH output. The compound does not raise cortisol or prolactin appreciably at standard doses, distinguishing it from GHRP-6 and other peptide secretagogues. Its 24-hour half-life allows once-daily oral dosing.
Dosing protocols
| Purpose | Route | Dosage | Frequency | Notes |
|---|---|---|---|---|
| muscle mass and body composition | oral | 10–25 mg | once daily | Start at 10 mg/day for 2 weeks to assess water retention and hunger response. Titrate to 25 mg/day. Most users cycle 8–12 weeks on, 4 weeks off. |
| sleep quality and GH pulse | oral | 12–25 mg | once daily at night | Taken 30–60 minutes before sleep to align with natural nocturnal GH pulse. Lower doses (12.5 mg) often sufficient for sleep benefit with fewer side effects. |
Dosing information is for educational purposes only. Consult a qualified healthcare professional before using any peptide.
Research summary
Multiple Phase 2 clinical trials have demonstrated that MK-677 significantly increases GH and IGF-1 levels and improves lean body mass in healthy elderly subjects. A 12-month trial at 25 mg/day showed increased fat-free mass and reduced LDL cholesterol. However, a cardiac safety study was terminated early due to increased heart failure events in elderly patients. No FDA approval has been granted. Long-term safety data in younger populations remain limited.
Side effects
Side effects vary by individual. This is not an exhaustive list. Report unusual symptoms to a healthcare professional.
Common stacks
Peptides commonly paired with MK-677 for synergistic effects.
Legal status
MK-677 is not a peptide and not subject to the 2023 FDA compounding ban. It is not a controlled substance in the US but is prohibited by WADA (S2 category). Sold legally as a research chemical; not approved for human consumption. The FDA has issued warning letters to supplement companies marketing it for human use.
Where to get it
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