Side-by-Side Comparison
Tesamorelin vs MK-677: Mechanism, Evidence & Safety Compared
An evidence-based side-by-side look at how Tesamorelin 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: Egrifta, TH9507
An FDA-approved GHRH analog used for HIV-associated lipodystrophy, with research into broader metabolic and cognitive applications.
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 | Tesamorelin | MK-677 |
|---|---|---|
| Primary mechanism | GHRH Receptor Agonism | Oral Ghrelin Receptor Agonism |
| FDA status | FDA Approved | Research Only |
| Evidence level | FDA Approved | Strong Clinical Evidence |
| Human trials | Yes (12+ indexed) | Yes (15+ indexed) |
| Studies indexed | 36 total (18 human, 8 animal) | 75 total (25 human, 30 animal) |
| Primary uses researched | Visceral fat reduction, HIV lipodystrophy, Cognitive function (research) | Growth hormone release, Sleep quality, Appetite stimulation, Bone density (research) |
| Administration routes | subcutaneous | oral |
| Molecular weight | 5135.93 Da | 528.67 Da |
| Amino acids | 44 | — |
| Category | growth hormone | growth hormone |
| WADA status | Prohibited | Prohibited |
Key differences
Mechanism. Tesamorelin 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. Tesamorelin 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. Tesamorelin sits at a higher evidence level (L5) than MK-677 (L4) under PeptideMark's L1–L5 methodology, which weighs study type, sample size, and replication.
Research focus. Published research on Tesamorelin has concentrated on visceral fat reduction, hiv lipodystrophy, cognitive function (research). Research on MK-677 has concentrated on growth hormone release, sleep quality, appetite stimulation. These research programs have limited overlap, and comparisons are most useful when readers are evaluating adjacent therapeutic goals.
Safety snapshot
| Attribute | Tesamorelin | MK-677 |
|---|---|---|
| Documented effects | 9 total | 9 total |
| Serious events | 0 | 0 |
| Common events | 5 | 4 |
| Black box warning | No | No |
| Contraindications | 4 listed | 4 listed |
| Drug interactions | 2 flagged | 2 flagged |
| Most common event | Injection site reactions | Increased appetite |
Strengths & limitations
Tesamorelin
Strengths
- FDA-approved with established regulatory record
- Strong evidence base (L5)
- Multiple human clinical trials (12+ 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
Tesamorelin
Tesamorelin, a Growth Hormone–Releasing Factor Analogue, Reduces Visceral Fat in HIV-Infected Patients
Falutz J, et al. · Annals of Internal Medicine (2007)
Tesamorelin reduced visceral adipose tissue by 15.4% compared to placebo, without worsening glucose tolerance.
PubMed 17909207REDUCE-1: Tesamorelin in HIV-Associated Lipodystrophy — A Randomized Controlled Trial
Grunfeld C, Thompson M, Brown SJ, et al. · AIDS (2006)
Tesamorelin reduced visceral AT by 18.3% versus 8.3% placebo (p<0.001); improvement sustained at 26 weeks post-treatment.
PubMed 16816556MK-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 Tesamorelin and MK-677?
Tesamorelin is an fda-approved ghrh analog used for hiv-associated lipodystrophy, with research into broader metabolic and cognitive applications. 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 (L5 vs L4), and the primary conditions for which each is researched.
Is Tesamorelin or MK-677 FDA approved?
Tesamorelin: FDA-approved in 2010 as Egrifta for the reduction of excess abdominal fat in HIV-infected patients with lipodystrophy. 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?
Tesamorelin has 36 indexed studies (18 human, 8 animal) and is rated FDA Approved. 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 Tesamorelin 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 Tesamorelin and MK-677 commonly stacked together?
There is no widely documented stacking protocol combining Tesamorelin 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, Tesamorelin or MK-677?
Tesamorelin has 9 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 Tesamorelin and MK-677 administered?
Tesamorelin is typically administered via subcutaneous. MK-677 is typically administered via oral. Route differences affect onset, peak levels, and patient convenience.
Which is better, Tesamorelin or MK-677?
"Better" depends on the therapeutic goal, regulatory context, and individual response. Tesamorelin is most researched for visceral fat reduction and hiv lipodystrophy; MK-677 is most researched for growth hormone release and sleep quality. FDA status also matters: FDA Approved for Tesamorelin 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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