Side-by-Side Comparison
Sermorelin vs MK-677: Mechanism, Evidence & Safety Compared
An evidence-based side-by-side look at how Sermorelin and MK-677 differ in mechanism, regulatory status, strength of the research base, and clinical application — compiled from the published literature and the FDA regulatory record.
Educational content only. This page is compiled from published research for reference and is not medical advice, diagnosis, or treatment. Readers should verify claims against primary sources and consult a qualified healthcare provider before making any health decisions. Full disclaimer.
Also: Geref, GHRH(1-29)NH2
A growth hormone-releasing hormone analog with a long history of clinical use for GH deficiency diagnosis and therapy.
MK-677
L4Also: Ibutamoren, Nutrobal, L-163,191
An oral ghrelin mimetic (not a peptide) that stimulates growth hormone release. Has extensive human data but has not achieved FDA approval.
Side-by-side comparison
| Attribute | Sermorelin | MK-677 |
|---|---|---|
| Primary mechanism | GHRH Receptor Agonism | Oral Ghrelin Receptor Agonism |
| FDA status | FDA Approved | Research Only |
| Evidence level | Strong Clinical Evidence | Strong Clinical Evidence |
| Human trials | Yes (15+ indexed) | Yes (15+ indexed) |
| Studies indexed | 51 total (22 human, 15 animal) | 75 total (25 human, 30 animal) |
| Primary uses researched | Growth hormone stimulation, Anti-aging, Sleep quality, Body composition | Growth hormone release, Sleep quality, Appetite stimulation, Bone density (research) |
| Administration routes | subcutaneous | oral |
| Molecular weight | 3357.93 Da | 528.67 Da |
| Amino acids | 29 | — |
| Category | growth hormone | growth hormone |
| WADA status | Prohibited | Prohibited |
Key differences
Mechanism. Sermorelin acts primarily through ghrh receptor agonism, while MK-677 acts primarily through oral ghrelin receptor agonism. This means they address different biological pathways even when targeting overlapping clinical goals.
Regulatory status. Sermorelin is classified as fda approved; MK-677 is classified as research only. Regulatory status drives availability, legality, and the standard of evidence required for specific therapeutic claims.
Evidence base. Both compounds currently sit at L4 (Strong Clinical Evidence) on PeptideMark's methodology.
Research focus. Published research on Sermorelin has concentrated on growth hormone stimulation, anti-aging, sleep quality. Research on MK-677 has concentrated on growth hormone release, sleep quality, appetite stimulation. There is meaningful overlap between the two research programs, which is why these compounds are frequently compared.
Safety snapshot
| Attribute | Sermorelin | MK-677 |
|---|---|---|
| Documented effects | 6 total | 9 total |
| Serious events | 0 | 0 |
| Common events | 1 | 4 |
| Black box warning | No | No |
| Contraindications | 3 listed | 4 listed |
| Drug interactions | 2 flagged | 2 flagged |
| Most common event | Injection site reactions | Increased appetite |
Strengths & limitations
Sermorelin
Strengths
- FDA-approved with established regulatory record
- Strong evidence base (L4)
- Multiple human clinical trials (15+ indexed)
Limitations
- Prohibited in competitive sport under WADA
MK-677
Strengths
- Strong evidence base (L4)
- Multiple human clinical trials (15+ indexed)
Limitations
- Not FDA-approved for any indication — research use only
- Prohibited in competitive sport under WADA
Representative studies
Sermorelin
Two years of continuous subcutaneous infusion of GHRH(1-29)NH2 in GH deficient adults
Vittone J, et al. · Pituitary (1997)
Two years of sermorelin treatment maintained increased IGF-1 levels and improved lean body mass in GH-deficient adults.
PubMed 9452117Sermorelin Acetate Treatment in Growth Hormone Deficient Children: 2-Year Randomized Double-Blind Trial
Laron Z, Parks JS, Adler GK, et al. · Journal of Clinical Endocrinology & Metabolism (1995)
Sermorelin increased mean height velocity from 4.2 to 8.1 cm/year and serum IGF-1 by 247% compared to baseline; sustained over 24 months.
PubMed 7852385MK-677
MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism
Murphy MG, Plunkett LM, Gertz BJ, et al. · Journal of Clinical Endocrinology & Metabolism (1998)
MK-677 25mg daily reversed diet-induced nitrogen wasting by increasing GH pulse amplitude and IGF-1 levels.
PubMed 9467534Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial
Nass R, Pezzoli SS, Oliveri MC, et al. · Annals of Internal Medicine (2008)
MK-677 increased GH and IGF-1 to youthful levels for 12 months but did not improve strength or function, and insulin sensitivity declined significantly.
PubMed 18981485Frequently asked
What is the main difference between Sermorelin and MK-677?
Sermorelin is a growth hormone-releasing hormone analog with a long history of clinical use for gh deficiency diagnosis and therapy. Its primary mechanism is ghrh receptor agonism. MK-677 is an oral ghrelin mimetic (not a peptide) that stimulates growth hormone release. has extensive human data but has not achieved fda approval. Its primary mechanism is oral ghrelin receptor agonism. The two differ in regulatory status (FDA Approved vs Research Only), strength of evidence (L4 vs L4), and the primary conditions for which each is researched.
Is Sermorelin or MK-677 FDA approved?
Sermorelin: Previously FDA-approved as a diagnostic agent for GH deficiency (Geref). The commercial product was discontinued but sermorelin remains available through compounding pharmacies. MK-677: Not FDA-approved. Non-peptide ghrelin mimetic (not technically a peptide, but commonly grouped with peptides). Has failed in clinical trials for growth hormone deficiency.
How does the evidence base compare?
Sermorelin has 51 indexed studies (22 human, 15 animal) and is rated Strong Clinical Evidence. MK-677 has 75 indexed studies (25 human, 30 animal) and is rated Strong Clinical Evidence. Evidence ratings reflect PeptideMark's L1–L5 methodology based on study type, sample size, and replication.
Can Sermorelin and MK-677 be compared directly?
Yes — both compounds share the growth hormone category, meaning head-to-head comparisons are meaningful for the same therapeutic targets. Direct head-to-head trials between peptides are rare, however, so most comparisons rely on separate trial datasets rather than direct RCT data.
Are Sermorelin and MK-677 commonly stacked together?
There is no widely documented stacking protocol combining Sermorelin and MK-677 in the peer-reviewed literature. Any combination use should be supervised by a qualified clinician familiar with both compounds' pharmacology and contraindications.
Which has a better-documented safety profile, Sermorelin or MK-677?
Sermorelin has 6 documented side effects (0 serious). MK-677 has 9 documented side effects (0 serious). Better documentation does not necessarily mean safer — FDA-approved drugs have more rigorous adverse-event reporting, while research-only compounds may appear "cleaner" simply because fewer controlled trials have captured events systematically.
How are Sermorelin and MK-677 administered?
Sermorelin is typically administered via subcutaneous. MK-677 is typically administered via oral. Route differences affect onset, peak levels, and patient convenience.
Which is better, Sermorelin or MK-677?
"Better" depends on the therapeutic goal, regulatory context, and individual response. Sermorelin is most researched for growth hormone stimulation and anti-aging; MK-677 is most researched for growth hormone release and sleep quality. FDA status also matters: FDA Approved for Sermorelin vs Research Only for MK-677. This page is educational — any decision to use either compound should be made with a qualified clinician who has reviewed your medical history.
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