MK-677 (Ibutamoren) is an orally active ghrelin-receptor agonist studied for raising growth hormone and IGF-1 levels without injection. Trials in older adults showed increased GH/IGF-1 and lean mass but also increased insulin resistance, fluid retention, and joint pain, and it has not been approved for any indication.
Benefits
MK-677 (ibutamoren) is an orally active, non-peptide ghrelin receptor agonist — mechanistically related to compounds like ipamorelin, but taken as a pill with a much longer duration of action. It has the most extensive human clinical trial history of any compound in this batch.
Body composition (healthy older adults, 2-year RCT, n=65): 25mg/day increased fat-free mass by 1.1kg over 12 months (vs. a 0.5kg decrease on placebo, P<0.001). Nass et al., Ann Intern Med, 2008
Bone turnover (elderly, n=187 across 3 sub-studies): 25mg/day for 9 weeks increased serum osteocalcin 29.4% and bone-specific alkaline phosphatase 10.4% (both P<0.001). Murphy et al., J Bone Miner Res, 1999
IGF-1 elevation: consistently and reliably raised across every trial found — the most replicated finding for this compound.
What it does not do: despite reliably raising IGF-1, MK-677 showed no cognitive or functional benefit in Alzheimer's disease in a 563-patient, 12-month RCT. Sevigny et al., Neurology, 2008
Dosage
25mg/day, oral, is the dose used across nearly every trial found — the 2-year body-composition RCT, the hip-fracture trial, and the Alzheimer's trial. This is an actual, repeatedly-trialed clinical dose, not a community-reported convention.
Side Effects
The most important safety finding in this entire research batch: a Phase IIb trial in elderly hip-fracture patients (n=123) was terminated early after 4 of 62 patients (6.5%) on MK-677 developed congestive heart failure, vs. 1 of 61 (1.7%) on placebo. The paper's own conclusion: MK-677 "has an unfavorable safety profile in this patient population." Adunsky et al., Arch Gerontol Geriatr, 2011
Separately, in healthy older adults over 2 years: fasting glucose increased (P=0.015), insulin sensitivity decreased, cortisol increased. Edema and muscle pain were reported as "transient" and "mild" in this population — notably milder than the hip-fracture trial's CHF finding, suggesting the cardiovascular risk may be population-dependent (elderly, post-fracture, likely pre-existing cardiovascular vulnerability) rather than a flat risk for all users.
This compound has real efficacy signals and a real, serious cardiovascular safety signal in a specific population — both equally well-sourced.
Results Timeline
Real human trial timepoints throughout: bone turnover markers significantly elevated by 9 weeks; fat-free mass and metabolic changes measured at 12 months, confirmed again at 24 months; the CHF safety signal emerged within a 24-week trial, serious enough to trigger early termination.
Is MK-677 FDA-approved?+
No. Trials in elderly patients for frailty and hip-fracture recovery did not lead to approval, partly due to side effects like insulin resistance and fluid retention.
How is MK-677 different from injectable GH secretagogues like CJC-1295?+
MK-677 is taken orally and acts on the ghrelin receptor, while CJC-1295 is injected and acts on the GHRH receptor — different pathways toward a similar GH-raising effect.
Is MK-677 banned in sport?+
Yes, as a growth-hormone secretagogue it is prohibited under WADA S2.
Why do people prefer this over injectable GHRPs?+
The obvious reason: it's oral, no injections at all. It also has a long half-life — around 24 hours — so once-daily dosing keeps levels steady, a real convenience difference from GHRPs needing multiple shots a day.
Is the water retention/bloating real?+
Yes — growth hormone promotes sodium retention in your kidneys, which shows up as temporary water weight and a bloated feeling. Most people at moderate doses (10-15mg) don't notice much of it, but it's one of the more commonly reported effects at higher doses.
Does it actually affect blood sugar?+
This is the one to genuinely pay attention to. GH reduces insulin sensitivity, so fasting glucose and HbA1c can climb while you're on it — the single most important thing to monitor, more so than water retention or appetite changes.
Why does it make some people feel sluggish?+
Fatigue and lethargy show up for some, especially at higher doses or early on — usually described as temporary rather than lasting, but real enough that most people start low rather than jumping to a full dose.
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