Overview
MK-677 is a growth hormone-related peptide. Non-peptide oral ghrelin mimetic.
With a half-life of ~1 days (24 hours), MK-677 supports less frequent dosing schedules. Taken orally, it has a bioavailability of approximately 95% via its primary route.
Half-life approximately 24 hours. Not a peptide despite common categorization with GH peptides. Non-suppressive to endogenous hormone production. One-compartment model.
Mechanism of Action
MK-677's pharmacological activity involves the following key pathways:
Oral GH Secretagogue
MK-677 is an orally active ghrelin mimetic that stimulates GH release by activating the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus.
Dosing Protocols
The following protocols represent commonly observed dosing patterns. These are observational summaries, not recommendations.
Dose
10 mg/day
Route
Oral
Frequency
Every other day
Duration
4-12 weeks
Dose
25 mg/day
Route
Oral
Frequency
Every other day
Duration
4-12 weeks
Frequently Asked Questions
What is MK-677 and how does it work?
MK-677 (Ibutamoren) is a non-peptide, orally active ghrelin receptor agonist that stimulates the pituitary gland to increase growth hormone (GH) secretion. It mimics the hunger hormone ghrelin by binding to GHS-R1a receptors in the hypothalamus, amplifying both the frequency and amplitude of natural GH pulses. This results in sustained elevations of GH and IGF-1 without requiring injections.
What is the half-life of MK-677 and when should it be taken?
MK-677 has an effective half-life of approximately 24 hours, with IGF-1 levels remaining elevated for the full day after a single oral dose. This allows for convenient once-daily dosing. Bedtime dosing is commonly observed because it aligns GH stimulation with the natural nocturnal GH pulse and reduces the impact of appetite stimulation during waking hours.
How long does MK-677 take to show effects?
Increased appetite is commonly reported within the first few days due to ghrelin receptor activation. Sleep quality improvements are typically observed within 1–2 weeks. IGF-1 levels have been observed to increase significantly by 2–4 weeks of consistent dosing. Body composition changes are generally reported over 8–12 weeks of use.
Does MK-677 cause water retention and increased appetite?
Increased appetite is one of the most commonly reported effects, appearing within the first few days as a direct consequence of ghrelin receptor activation. Mild water retention is frequently observed around weeks 2–4, which can produce a fuller appearance. Both effects are dose-dependent and are generally more pronounced at higher doses. The appetite increase tends to moderate after the first few weeks.
Does MK-677 suppress natural growth hormone production?
Unlike exogenous GH injections, MK-677 does not suppress endogenous growth hormone production. It works by stimulating the body's own pituitary gland to release GH in its natural pulsatile pattern, preserving normal feedback regulation. This is why post-cycle therapy (PCT) is not typically observed after discontinuation.
How does MK-677 affect sleep quality?
Clinical research has observed that MK-677 increases deep sleep (stage IV) duration and REM sleep. These effects are attributed to the interaction between ghrelin pathways and sleep architecture, which is one reason bedtime dosing is the most commonly reported timing. Improvements in sleep quality are typically noted within the first 1–2 weeks of use.