MK-677
Well studiedGhrelin Receptor Agonist | Oral Growth Hormone Secretagogue
Oral compound activating ghrelin receptors to trigger growth hormone release while preserving natural production.
Molecular & research data
- Molecular weight
- 624.77 Da
- Half-life
- ~24 hours
- Primary targets
- ghrelin-receptor
- Routes (research)
- Oral
- Storage
- Room temperature in cool, dry place; no refrigeration required
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.
Mechanism of action
Selectively binds GHS-R1a receptors in hypothalamus and pituitary, triggering pulsatile growth hormone release while maintaining natural circadian patterns.
Key research findings
- 97% increase in 24-hour growth hormone secretion
- 40-72% elevation in IGF-1 levels
- Enhanced sleep quality with improved REM patterns
- Preferential lean tissue gains of 1.1-2.7kg over 8-12 months
- 15% basal metabolic rate increase within 2 weeks
- Oral administration (no injections required)
Research applications
Growth Hormone
- GH Restoration — Restores youthful growth hormone levels in elderly subjects with 97% increase in 24-hour secretion.
- IGF-1 Enhancement — Sustained 40-72% IGF-1 elevation over extended periods.
- Sleep Enhancement — 20% REM increase in younger adults; 50% improvement in elderly.
Body Composition
- Muscle Preservation — Demonstrates +2.69g/day nitrogen retention versus -8.97g/day placebo, protecting lean mass during caloric restriction.
- Fat-Free Mass — Increases fat-free mass with preferential lean tissue accrual.
- Metabolic Rate — 15% basal metabolic rate elevation documented at 2 weeks.
Bone Health
- Bone Formation — 39-45% increase in bone formation markers within 6-8 weeks.
MK-677 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
- [1]Effects 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 menJournal of Clinical Endocrinology & Metabolism
- [2]Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretagogue (MK-677) in healthy elderly subjectsJournal of Clinical Endocrinology & Metabolism
- [3]Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in manNeuroendocrinology
- [4]MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolismJournal of Clinical Endocrinology & Metabolism
- [5]Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditureJournal of Clinical Endocrinology & Metabolism
- [6]Oral administration of the growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adultsJournal of Bone and Mineral Research
- [7]Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trialAnnals of Internal Medicine
- [8]FDA Warning: Potential Health Risks of MK-677DEA Get Smart About Drugs
- [9]LGD-4033 and MK-677 use impacts body composition, circulating biomarkers, and skeletal muscle androgenic hormone and receptor content: A case reportPhysiological Reports
- [10]Hepatotoxicity induced by MK-677BMJ Case Reports
Related peptides
Ipamorelin
In clinical trialsSelective ghrelin-mimetic GHRP
Ipamorelin is a selective growth hormone releasing peptide (GHRP) that stimulates GH release with minimal effect on cortisol, prolactin, or appetite, making it the cleanest of the classic GHRPs.
GHRP-2
In clinical trialsPotent ghrelin-mimetic GH secretagogue
GHRP-2 (pralmorelin) is a potent growth hormone releasing peptide used clinically as a diagnostic agent in some countries, known for strong GH release with moderate appetite and cortisol effects.
TB-500
PreclinicalSynthetic Thymosin Beta-4 studied for repair & cell migration
TB-500 is a synthetic version of Thymosin Beta-4 (or its active fragment), a naturally occurring peptide studied for its role in actin regulation, cell migration, and tissue repair.
BPC-157
PreclinicalPentadecapeptide studied for tissue repair
BPC-157 is a synthetic 15-amino-acid peptide derived from a protein found in gastric juice, studied extensively in animal models for accelerated healing of tendon, ligament, muscle, and gut tissue.
Last reviewed: 2026-06-26. Information is provided for research and educational reference only — see our disclaimer.