Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of GHRP-6 and MK-677 — mechanism, side effects, legal status, and pricing.
GHRP-6 is a synthetic hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) growth hormone secretagogue and ghrelin receptor agonist. Developed by Bowers and Momany and first described in 1984, it was the first synthetic GHRP characterized and is defined by its pronounced appetite-stimulating effect — the strongest of any clinically studied GHRP. It has never been approved by the FDA or any regulatory agency and remains a research-only compound used off-label in the grey market.
MK-677 (ibutamoren, MK-0677, L-163,191) is an orally active, non-peptide small-molecule growth hormone secretagogue developed by Merck in the 1990s. It is a spiropiperidine ghrelin-receptor (GHSR-1a) agonist — not a peptide and not a SARM, though it is commonly misclassified as both in grey-market retail. Merck discontinued development after mixed efficacy and adverse metabolic / cardiovascular findings; it is not FDA-approved.
GHRP-6
MK-677
Category
Legal Status
Mechanism
Half-life
Side Effects
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GHRP-6
MK-677
No pricing data yet.
Check MK-677 prices →COA corpus from Disclosed Labs — independently tested batches only.
GHRP-6
13
COAs
99.4%
Avg purity
4
Labs
MK-677
5
COAs
98.3%
Avg purity
3
Labs
GHRP-6 is among peptides under FDA review for the Category 1 (503A) list; if added, it would require a prescription to be compounded by registered 503A/503B pharmacies — not yet authorized. MK-677 remains research-only. In April 2026 the FDA removed 12 peptides from Category 2, which does not place them on the Category 1 list or authorize compounding. The FDA's Pharmacy Compounding Advisory Committee is advisory and meets July 23–24, 2026 to review nominations and make recommendations to the FDA.
GHRP-6 was first characterized by Bowers, Momany, Reynolds, and Hong in Endocrinology (1984, PMID 6714155), establishing it as the first synthetic peptide to specifically release GH via a non-GHRH mechanism — a key tool in the later discovery of the ghrelin receptor. Ghigo et al. (European Journal of Endocrinology, 1997, PMID 9186261) reviewed the GHRP class and confirmed GH, ACTH/cortisol, and prolactin co-stimulation in humans. Berlanga et al. (Clinical Science, 2007, PMID 16989643) demonstrated ~78% infarct-mass reduction in a porcine myocardial infarction model via antioxidant mechanisms, and Berlanga-Acosta et al. (Clinical Medicine Insights: Cardiology, 2017, PMID 28469491) reviewed the cytoprotective GHRP literature across cardiac, neuronal, and hepatic tissues. GHRP-6 has never been approved for any clinical indication; its intense appetite stimulation and cortisol/prolactin co-release limit its clinical utility compared with ipamorelin.
Key references
MK-677 has meaningful human data from Merck-sponsored Phase I/II trials. Murphy et al. (JCEM 1998, PMID 9467534) showed 25 mg MK-677 reversed nitrogen wasting during caloric restriction in healthy adults. Svensson et al. (JCEM 1998, PMID 9467542) reported ~40% IGF-1 elevation, increased fat-free mass, and higher energy expenditure over 8 weeks in obese men. Copinschi et al. (Neuroendocrinology 1997, PMID 9349662) documented improved slow-wave and REM sleep in young and older adults. Nass et al. (Ann Intern Med 2008, PMID 18981485) — the pivotal 2-year randomized trial in 65 healthy older adults — restored GH and IGF-1 to young-adult levels and increased fat-free mass, but produced modest fasting glucose elevation and insulin resistance. The Adunsky et al. Phase IIb hip-fracture trial (Arch Gerontol Geriatr 2011, PMID 21067829) was stopped early after a congestive-heart-failure safety signal (4/62 ibutamoren vs 1/60 placebo). Merck discontinued development. MK-677 is commonly mislabeled as a 'SARM' in grey-market retail — it is not; it is a ghrelin-receptor agonist and oral GH secretagogue. It has never been FDA-approved.
GHRP-6 and MK-677 are both in the Performance category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Contraindications
Lab Testing
Key references
Disclosed Labs