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 MK-677 and Sermorelin — mechanism, dosing, side effects, legal status, and pricing.
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.
Sermorelin is a synthetic analog of growth hormone-releasing hormone (GHRH) consisting of the first 29 amino acids of the 44-aa native hormone — the shortest fragment that retains full biological activity. It was FDA-approved in the 1990s as Geref (EMD Serono) for diagnostic testing of pituitary GH reserve and later for pediatric idiopathic GH deficiency, but was withdrawn from the US market in 2008–2009 at the manufacturer's request for commercial reasons (not safety or efficacy). It remains on the FDA Category 1 list of bulk substances nominated for use in 503A compounding, where it is now widely prescribed off-label for adult GH insufficiency and "anti-aging" indications.
MK-677
Sermorelin
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Legal Status
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MK-677
No pricing data yet.
Check MK-677 prices →Sermorelin
COA corpus from Disclosed Labs — independently tested batches only.
MK-677
5
COAs
98.3%
Avg purity
3
Labs
Sermorelin
72
COAs
99.4%
Avg purity
10
Labs
Sermorelin 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.
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.
Key references
Sermorelin was FDA-approved in the 1990s as Geref for the GHRH stimulation test of pituitary function and, at higher doses, for pediatric idiopathic GHD. The principal review of pediatric Geref data is Prakash & Goa (BioDrugs 1999; PMID 18031173). In adults, Vittone et al. (Metabolism 1997; PMID 9005976) showed nightly sermorelin in healthy elderly men raised IGF-1 and modestly increased lean mass, and Khorram, Laughlin & Yen (J Clin Endocrinol Metab 1997; PMID 9141536) demonstrated that 16 weeks of nightly [Nle27]GHRH(1-29) in 19 subjects aged 55-71 restored GH/IGF-1 toward young-adult levels with small gains in lean mass and skin thickness. Walker (Clin Interv Aging 2006; PMID 18046908) reviewed the rationale for sermorelin as a more physiologic alternative to rhGH in adult GH insufficiency. EMD Serono discontinued Geref in 2008; FDA withdrew NDA approvals in 2009 and affirmed in 2013 that this was for commercial — not safety or efficacy — reasons. Unlike exogenous GH, sermorelin has not been associated with reports of acromegaly because endogenous feedback limits peak GH.
MK-677 and Sermorelin 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.
Dosing Notes
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Key references
Disclosed Labs