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Comparison

MK-677 vs Somatropin

MK-677 is gHRPs & ghrelin mimetics; Somatropin is IGF & growth factors. They are compared here because they are frequently considered against each other, not because they act alike.

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

MK-677 Somatropin
Class GHRPs & ghrelin mimetics IGF & growth factors
Evidence Clinical trials Regulator approved
Human trials ~22 ~200
Half-life ~24 hours ~3-5 hours (subcutaneous)
Reported range 10-25 mg 200 mcg - 1 mg
Frequency Once daily Once daily, indication-dependent
Routes Oral Subcutaneous, Intramuscular
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, Short stature syndromes, HIV wasting, Short bowel syndrome
Reported side effects Increased appetite, Water retention, Reduced insulin sensitivity, Lethargy, Numbness in extremities Peripheral oedema, Arthralgia, Carpal tunnel syndrome, Insulin resistance, Myalgia

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.

Somatropin

Somatropin is recombinant 191-amino-acid human growth hormone, identical in sequence to the pituitary hormone. It acts directly at growth hormone receptors in liver and peripheral tissue, driving hepatic IGF-1 production, lipolysis and nitrogen retention. Unlike the secretagogues it bypasses pituitary regulation entirely, which is both why it is more predictable and why it carries the greater risk of supraphysiologic exposure and negative feedback on endogenous production.

MK-677 vs Somatropin: common questions

What is the difference between MK-677 and Somatropin?

MK-677 is gHRPs & ghrelin mimetics and Somatropin is IGF & growth factors, 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. Somatropin: Recombinant human growth hormone itself, the reference compound every secretagogue on this site is compared against.

Which has stronger evidence, MK-677 or Somatropin?

Somatropin has the stronger evidence base (regulator approved, about 200 human studies) compared with MK-677 (clinical trials).

Are MK-677 and Somatropin FDA approved?

Only Somatropin is FDA approved (Paediatric growth hormone deficiency; Adult growth hormone deficiency; Turner syndrome; Prader-Willi syndrome; Growth failure associated with chronic kidney disease; Children born small for gestational age without catch-up growth; Idiopathic short stature; SHOX deficiency; Noonan syndrome; HIV-associated wasting or cachexia (Serostim); Short bowel syndrome (Zorbtive, no longer marketed)). 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 137552069) ↗ · structure, identifiers, synonyms
  6. DailyMed: FDA-approved labeling for Somatropin ↗ · indications, dosing, warnings as approved
  7. FDA Drugs@FDA database ↗ · approval history
  8. CAS Registry Number 12629-01-5 ↗ · 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. Bidlingmaier M, Strasburger CJ. Growth hormone.Handb Exp Pharmacol 2010.PubMed 20020365 · doi:10.1007/978-3-540-79088-4_8
  10. Deal CL, Steelman J, Vlachopapadopoulou E, et al.. Efficacy and Safety of Weekly Somatrogon vs Daily Somatropin in Children With Growth Hormone Deficiency: A Phase 3 Study.J Clin Endocrinol Metab 2022.PubMed 35405011 · doi:10.1210/clinem/dgac220
  11. Bidlingmaier M, Wu Z, Strasburger CJ. Doping with growth hormone.J Pediatr Endocrinol Metab 2001.PubMed 11592563 · doi:10.1515/jpem-2001-0802
  12. Pfäffle R, Kiess W. GH and IGF-1 Replacement in Children.Handb Exp Pharmacol 2020.PubMed 31932988 · doi:10.1007/164_2019_337
  13. Wang K, Ye F, Wang DY, et al.. Aromatase inhibitors for short stature in male children and adolescents treated with growth hormone: a meta-analysis of randomized controlled trials.BMC Pediatr 2024.PubMed 39696162 · doi:10.1186/s12887-024-05301-0
  14. Thornton PS, Maniatis AK, Aghajanova E, et al.. Weekly Lonapegsomatropin in Treatment-Naïve Children With Growth Hormone Deficiency: The Phase 3 heiGHt Trial.J Clin Endocrinol Metab 2021.PubMed 34272849 · doi:10.1210/clinem/dgab529
  15. Blunden C, Nasomyont N, Backeljauw P. Growth Hormone Therapy for Turner Syndrome.Pediatr Endocrinol Rev 2018.PubMed 30378785 · doi:10.17458/per.vol16.2018.bnb.ghtherapyturnersyndrome
  16. Goldsmith DR, Wagstaff AJ. Mammalian cell-derived somatropin : a review of its use in the management of HIV-associated wasting.Drugs 2006.PubMed 16526830 · doi:10.2165/00003495-200666030-00014

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.