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Comparison

MK-677 vs Sermorelin

MK-677 is gHRPs & ghrelin mimetics; Sermorelin is GHRH analogs. They are compared here because they are frequently considered against each other, not because they act alike.

On published evidence alone, Sermorelin is the better documented of the two (regulator approved). That is a statement about the state of the literature, not a recommendation.

MK-677 Sermorelin
Class GHRPs & ghrelin mimetics GHRH analogs
Evidence Clinical trials Regulator approved
Human trials ~22 ~20
Half-life ~24 hours ~10-20 minutes
Reported range 10-25 mg 200-500 mcg
Frequency Once daily Once daily at bedtime
Routes Oral Subcutaneous
FDA approved No Yes
Research use only Yes No
Banned in sport Yes Yes
Studied for Growth hormone elevation, Appetite stimulation, Sleep depth, Lean mass Growth hormone deficiency diagnosis and paediatric treatment, Age-related GH decline, Sleep quality, Body composition
Reported side effects Increased appetite, Water retention, Reduced insulin sensitivity, Lethargy, Numbness in extremities Injection-site erythema, Flushing, Headache, Transient dizziness

MK-677

MK-677 is a spiropiperidine growth hormone secretagogue receptor agonist, not a peptide, though it is almost always discussed alongside them because it targets the same receptor as the GHRPs. Oral bioavailability and a roughly 24-hour half-life produce sustained elevation of GH and IGF-1 from once-daily dosing. The same sustained exposure drives its two characteristic problems: marked appetite increase and a consistent reduction in insulin sensitivity.

Sermorelin

Sermorelin is a truncated analog of growth-hormone-releasing hormone comprising residues 1-29, the minimum sequence required for receptor activation. It binds the GHRH receptor on anterior pituitary somatotrophs and stimulates synthesis and pulsatile release of endogenous growth hormone. Because it acts upstream on the pituitary rather than replacing growth hormone directly, release remains subject to negative feedback from somatostatin and IGF-1, which is the usual argument for a lower risk of supraphysiologic exposure than exogenous hGH.

MK-677 vs Sermorelin: common questions

What is the difference between MK-677 and Sermorelin?

MK-677 is gHRPs & ghrelin mimetics and Sermorelin is GHRH analogs, so they act on different pathways. MK-677: An orally active, long-acting ghrelin-receptor agonist. Frequently grouped with peptides but chemically a non-peptide small molecule. Sermorelin: The first 29 amino acids of endogenous growth-hormone-releasing hormone, and the shortest fragment that retains full biological activity.

Which has stronger evidence, MK-677 or Sermorelin?

Sermorelin has the stronger evidence base (regulator approved, about 20 human studies) compared with MK-677 (clinical trials).

Are MK-677 and Sermorelin FDA approved?

Only Sermorelin is FDA approved (Diagnostic assessment of pituitary GH secretory capacity (Geref); Treatment of idiopathic growth hormone deficiency in children with growth failure (Geref, approved 1997; discontinued by the manufacturer in 2008, not for safety reasons)). MK-677 is not approved for any indication.

References

Regulatory and primary sources

  1. PubChem compound record (CID 6450830) ↗ · structure, identifiers, synonyms
  2. WADA Prohibited List ↗ · current year
  3. FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
  4. CAS Registry Number 159752-10-0 ↗ · chemical identity
  5. PubChem compound record (CID 16132413) ↗ · structure, identifiers, synonyms
  6. DailyMed: FDA-approved labeling for Sermorelin ↗ · indications, dosing, warnings as approved
  7. FDA Drugs@FDA database ↗ · approval history
  8. CAS Registry Number 86168-78-7 ↗ · chemical identity

Published literature

  1. Ghigo E, Arvat E, Muccioli G, et al.. Growth hormone-releasing peptides.Eur J Endocrinol 1997.PubMed 9186261 · doi:10.1530/eje.0.1360445
  2. Murphy MG, Plunkett LM, Gertz BJ, et al.. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism.J Clin Endocrinol Metab 1998.PubMed 9467534 · doi:10.1210/jcem.83.2.4551
  3. Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues.Sex Med Rev 2018.PubMed 28400207 · doi:10.1016/j.sxmr.2017.02.004
  4. Camanni F, Ghigo E, Arvat E. Growth hormone-releasing peptides and their analogs.Front Neuroendocrinol 1998.PubMed 9465289 · doi:10.1006/frne.1997.0158
  5. Stawerska R. New directions in growth hormone treatment in children.Pediatr Endocrinol Diabetes Metab 2025.PubMed 41693185 · doi:10.5114/pedm.2025.158544
  6. Muccioli G, Broglio F, Valetto MR, et al.. Growth hormone-releasing peptides and the cardiovascular system.Ann Endocrinol (Paris) 2000.PubMed 10790589
  7. Camiña JP, Carreira MC, Micic D, et al.. Regulation of ghrelin secretion and action.Endocrine 2003.PubMed 14610293 · doi:10.1385/ENDO:22:1:5
  8. Smith RG, Sun Y, Jiang H, et al.. Ghrelin receptor (GHS-R1A) agonists show potential as interventive agents during aging.Ann N Y Acad Sci 2007.PubMed 18056963 · doi:10.1196/annals.1404.023
  9. Rahman OF, Lee SJ, Seeds WA. Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.J Am Acad Orthop Surg Glob Res Rev 2026.PubMed 41490200 · doi:10.5435/JAAOSGlobal-D-25-00236
  10. Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance.Sports Med 2026.PubMed 41966639 · doi:10.1007/s40279-026-02437-0
  11. Memdouh S, Gavrilović I, Ng K, et al.. Advances in the detection of growth hormone releasing hormone synthetic analogs.Drug Test Anal 2021.PubMed 34665524 · doi:10.1002/dta.3183
  12. Walker RF. Sermorelin: a better approach to management of adult-onset growth hormone insufficiency?.Clin Interv Aging 2006.PubMed 18046908 · doi:10.2147/ciia.2006.1.4.307
  13. Ramirez G, Herrera R, Pineda D, et al.. The effects of high altitude on hypothalamic-pituitary secretory dynamics in men.Clin Endocrinol (Oxf) 1995.PubMed 7641401 · doi:10.1111/j.1365-2265.1995.tb01887.x
  14. Coutinho LFD, DE Oliveira Neves LF, Camilo RP. A new era of doping? Use of peptide and peptide-analog drugs in recreational and professional sport and bodybuilding: a critical review.J Sports Med Phys Fitness 2026.PubMed 41880199 · doi:10.23736/S0022-4707.26.17773-1
  15. Popovic V, Pekic S, Golubicic I, et al.. The impact of cranial irradiation on GH responsiveness to GHRH plus GH-releasing peptide-6.J Clin Endocrinol Metab 2002.PubMed 11994347 · doi:10.1210/jcem.87.5.8485
  16. Saenger P, Pescovitz OH, Bercu BB, et al.. Outcome of growth hormone therapy in children with growth hormone deficiency showing an inadequate response to growth hormone-releasing hormone.Endocrine 2001.PubMed 11572326 · doi:10.1385/ENDO:15:1:051

Literature retrieved from PubMed on October 16, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.

Read this first This page compares published reference data. It is not medical advice and not a recommendation to use either compound. Several compounds documented on this site are not approved for human use.