MK-677
Ghrelin Receptor Agonist · Oral Growth Hormone Secretagogue
Oral compound activating ghrelin receptors to trigger growth hormone release while preserving natural production. Achieves superior oral bioavailability exceeding 60% with a 24-hour half-life, making it unique among GH secretagogues for its convenient once-daily oral dosing.
Overview
Oral compound activating ghrelin receptors to trigger growth hormone release while preserving natural production. Achieves superior oral bioavailability exceeding 60% with a 24-hour half-life, making it unique among GH secretagogues for its convenient once-daily oral dosing.
Selectively binds GHS-R1a receptors in hypothalamus and pituitary, triggering pulsatile growth hormone release while maintaining natural circadian patterns.
Research indications
What the compound has been studied for, grouped by body system. Effect size is the reported magnitude where it was measured — not a recommendation.
Restores youthful growth hormone levels in elderly subjects with 97% increase in 24-hour secretion.
Sustained 40-72% IGF-1 elevation over extended periods.
20% REM increase in younger adults; 50% improvement in elderly.
Demonstrates +2.69g/day nitrogen retention versus -8.97g/day placebo, protecting lean mass during caloric restriction.
Increases fat-free mass with preferential lean tissue accrual.
15% basal metabolic rate elevation documented at 2 weeks.
39-45% increase in bone formation markers within 6-8 weeks.
A large effect in a weak study and a small effect in a strong one are different things. Effect size is never evidence of use in people.
- Class
- Non-peptide ghrelin receptor agonist
- Molecular weight
- 624.77 Da
- Half-life
- ~24 h
- Typical dose
- Start 12.5mg daily, increase to 25mg based on tolerance
- Frequency
- Once daily, preferably at bedtime on empty stomach
- Cycle length
- 8-12 weeks for body composition goals
- Storage
- Room temperature in cool, dry place; no refrigeration required
Molecular data
- Type
- Non-peptide ghrelin receptor agonist
- Molecular weight
- 624.77 Da
- Half-life
- 1440 min
Dosing reference
Doses reported in the literature and by suppliers. These are a record of what has been used in research — reference, never instruction.
| Context | Route | Amount | Frequency |
|---|---|---|---|
| Body composition/anti-aging | Oral (bedtime, empty stomach) | 25mg | 1x daily |
| Sleep quality improvement | Oral (30 minutes before bed) | 25mg | 1x nightly |
| Conservative initiation | Oral (assess tolerance) | 12.5mg | 1x daily |
Interactions
Complementary GH pathways providing combined pulsatile and baseline elevation.
Both stimulate GH release through different mechanisms.
MK-677 baseline elevation combines with GHRP-2 pulsatile spikes.
Non-competing mechanisms enhancing recovery effects.
Systemic growth factors complement localized healing.
Redundant effects without proportional benefits.
MK-677 decreases insulin sensitivity; requires blood glucose monitoring.
Case report documents 85.7% testosterone suppression and significant liver enzyme elevation when combined.
Quality checklist
- ✓Pharmaceutical-grade capsules with professional labeling
- ✓Batch numbers and expiration dates
- ✓Third-party testing documentation
- ✓Certificate of analysis showing >98% purity
- !Products labeled 'for research only' may lack quality control
- ×Dietary supplement claims (FDA prohibits MK-677 in supplements)
- ×Unknown purity or source without certificates of analysis
- ×Unusually low prices suggesting counterfeit product
What to expect
Safety
- Appetite stimulation (>50% of users)
- Water retention (30-40%)
- Lethargy (20-30%)
- Fasting glucose elevation (5-15mg/dL)
- Note on testosterone suppression: at doses up to 20 mg daily, MK-677 is unlikely to cause significant testosterone suppression on its own. Above 20 mg daily, the likelihood of suppression and other side effects (insulin resistance, water retention, lethargy) increases. The case report documenting 85.7% testosterone suppression involved co-administration with LGD-4033, a SARM known to be profoundly suppressive, making the SARM the likely primary driver of that suppression.
- Shortness of breath, chest pain, or unusual fatigue
- Blood glucose levels >100mg/dL or diabetes symptoms
- Liver enzyme elevation (ALT/AST >2x upper normal)
- Severe fluid retention or unexplained swelling
- Any concerning cardiovascular symptoms
- Heart disease or congestive heart failure
- Diabetes or pre-diabetes
- Active cancer
- Severe cardiovascular disease
- Pregnancy or breastfeeding
FAQ
Why is MK-677 oral when most peptides are injected?
MK-677 is not actually a peptide—it's a small-molecule non-peptide ghrelin receptor agonist with excellent oral bioavailability (>60%) and a 24-hour half-life. This allows convenient once-daily oral dosing without injections, making it uniquely practical among GH secretagogues.
Does MK-677 increase testosterone suppression when combined with SARMs?
At doses up to 20mg daily, MK-677 alone causes minimal testosterone suppression. However, one case report documented 85.7% testosterone suppression when combined with LGD-4033 (a SARM). The SARM was likely the primary driver of suppression, not MK-677.
How much does MK-677 increase appetite?
Appetite stimulation affects >50% of users at 25mg doses. This is direct ghrelin mimicry—the same mechanism that increases GH. If appetite stimulation is problematic, reduce dose to 12.5mg or use ipamorelin instead for cleaner GH elevation without hunger.
Does MK-677 cause water retention?
Yes. 30-40% of users experience water retention from MK-677's GH stimulation and sodium retention effects. This appears within the first 2-4 weeks. Sodium management and adequate hydration help minimize bloating, and effects often diminish over time as the body adapts.
References
- 1Effects of a 7-day treatment with a novel, orally active, growth hormone (GH) secretagogue, MK-677, on 24-hour GH profiles, insulin-like growth factor I, and adrenocortical function in normal young menCopinschi, G., et al. · Journal of Clinical Endocrinology & Metabolism · 1996
Randomized, double-blind crossover in 9 healthy young men. 7-day oral MK-677 (5 and 25mg) increased 24-hour GH profiles dose-dependently while preserving circadian patterns.
human-rctPubMed 8768828 ↗ - 2Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretagogue (MK-677) in healthy elderly subjectsChapman, I.M., et al. · Journal of Clinical Endocrinology & Metabolism · 1996
Randomized, double-blind trial in 32 elderly subjects (64-81 years). 25mg/day MK-677 for up to 4 weeks increased mean 24-hour GH by 97% and restored IGF-I concentrations to young adult levels.
human-rctPubMed 8954023 ↗ - 3Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in manCopinschi, G., et al. · Neuroendocrinology · 1997
In young adults, 25mg MK-677 increased stage IV sleep duration by 50% and REM sleep by 20%. In older adults, REM sleep increased nearly 50% with decreased REM latency. Sleep deviations dropped from 42% to 8%.
reviewPubMed 9349662 ↗ - 4Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditureChapman, I.M., et al. · Journal of Clinical Endocrinology & Metabolism · 1998
24 obese males treated with 25mg/day for 8 weeks showed sustained increases in GH, IGF-I, fat-free mass, and a transient increase in basal metabolic rate at 2 weeks.
reviewPubMed 9467542 ↗ - 5MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolismMurphy, M.G., et al. · Journal of Clinical Endocrinology & Metabolism · 1998
Double-blind crossover in 8 healthy volunteers under caloric restriction. 25mg/day MK-677 for 7 days reversed nitrogen wasting (+2.69g/day vs -8.97g/day placebo) and significantly increased IGF-I.
reviewPubMed 9467534 ↗ - 6Oral administration of the growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adultsMurphy, M.G., et al. · Journal of Bone and Mineral Research · 1999
187 elderly adults (65+) across three placebo-controlled studies. 9 weeks of MK-677 increased serum osteocalcin by 29.4%, bone-specific alkaline phosphatase by 10.4%, and urinary NTX by 22.6%.
human-rctPubMed 10404019 ↗ - 7Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trialNass, R., et al. · Annals of Internal Medicine · 2008
12-month RCT in 65 healthy adults (60-81 years). MK-677 increased GH and IGF-I to young adult levels, increased fat-free mass while placebo group declined, and was generally well tolerated.
human-rctPubMed 18981485 ↗