Ipamorelin vs MK-677.
Quick Verdict
MK-677 is an oral GH secretagogue offering convenience and 24-hour IGF-1 elevation, while Ipamorelin is an injectable GHRP with a cleaner side-effect profile — no cortisol or prolactin elevation. MK-677 causes significant appetite increase and potential insulin resistance; Ipamorelin does not.
Side-by-Side Analysis
| Dimension | Ipamorelin | MK-677 |
|---|---|---|
| Category | GHRP | GH Secretagogue (Oral) |
| Mechanism | Selective GH secretagogue that mimics ghrelin at the GHS receptor. | Non-peptide ghrelin receptor (GHSR1a) agonist that stimulates prolonged, pulsatile growth hormone release from the pituitary gland. |
| Half-Life | ~2 hours | ~1 day |
| Route | SubQ | Oral |
| Typical Dose | 300–300 mcg | 12500–12500 mcg |
| Frequency | 7x/wk | 7x/wk |
| Evidence Level | Moderate | Moderate |
| Indexed Studies | 20+ indexed | 20+ indexed |
| FDA Status | Approved | Approved |
| Lowest Price | $50.00 / 5mg via Ascension Peptides | — |
Mechanism of Action Comparison
How Ipamorelin Works
Ipamorelin Ipamorelin is a selective growth-hormone-releasing peptide studied for stimulating clean GH pulses without raising cortisol or prolactin, making it one of the safest GH peptides available.
Selective GH secretagogue that mimics ghrelin at the GHS receptor. Does not significantly raise cortisol or prolactin, making it one of the most selective GH-releasing peptides.
How MK-677 Works
MK-677 MK-677 (Ibutamoren) is an orally bioavailable growth hormone secretagogue studied for sustainably elevating GH and IGF-1 levels over 24 hours with a single daily pill.
Non-peptide ghrelin receptor (GHSR1a) agonist that stimulates prolonged, pulsatile growth hormone release from the pituitary gland. Unlike injectable GH peptides, MK-677 is orally bioavailable with a ~24-hour half-life, enabling once-daily dosing. Increases IGF-1 levels for up to 12 months without desensitization of the GH axis. Does not suppress natural GH secretion patterns or affect cortisol levels at standard doses.
Key Mechanistic Difference
Ipamorelin operates as a ghrp, while MK-677 functions as a gh secretagogue (oral) — these are fundamentally different pharmacological approaches. MK-677 has a significantly longer half-life (~1 day) compared to Ipamorelin (~2 hours), which impacts dosing frequency and sustained activity.
Research Evidence
Ipamorelin
20 studies- Ipamorelin selective GH release original characterizationRaun et al. (Eur. J. Endocrinol.): First characterization showing Ipamorelin releases GH potently and selectively withou…Moderate
- Ipamorelin PK/PD modeling in healthy human volunteersDose-escalation study in healthy humans demonstrates Ipamorelin induces single-episode GH release with peak at ~0.67 hou…Moderate
- Ipamorelin and longitudinal bone growth in ratsSvensson et al. show Ipamorelin induces dose-dependent longitudinal bone growth and counters glucocorticoid-induced decr…Preclinical
MK-677
20 studies- MK-677 increases GH and IGF-1 without altering cortisol in healthy elderlyChapman et al. (J. Clin. Endocrinol. Metab.): 25mg daily MK-677 for 2 weeks in healthy elderly subjects restored IGF-1 a…Moderate
- MK-677 2-year study: sustained IGF-1 elevation and body composition effectsNass et al. (J. Clin. Endocrinol. Metab.): 2-year RCT in 65 healthy elderly adults. 25mg/day MK-677 increased GH and IGF…Strong
- MK-677 increases fat-free mass in healthy obese malesSvensson et al. (J. Clin. Endocrinol. Metab.): 8-week RCT in obese males. 25mg/day MK-677 significantly increased GH sec…Moderate
Vendor Pricing
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Frequently Asked Questions
Can I take Ipamorelin and MK-677 together?▼
No direct interaction data is available for this specific pair. They target different receptor systems, suggesting they could potentially be combined, but no published protocol validates this combination.
Which has more research evidence — Ipamorelin or MK-677?▼
Ipamorelin has 20 indexed studies (highest evidence: Moderate). MK-677 has 20 indexed studies (highest evidence: Moderate). Both have comparable research coverage.
Which is better for muscle growth — Ipamorelin or MK-677?▼
Both are researched for muscle growth. Ipamorelin addresses this via gh release, muscle growth, recovery without cortisol spike. MK-677 approaches it through sustained gh/igf-1 elevation, muscle growth, improved sleep, bone density, oral dosing convenience. The optimal choice depends on your specific research protocol and which mechanism aligns with your objectives.
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Research Use Only — Not Medical Advice
This comparison is provided for educational and research purposes only. It does not constitute medical, prescribing, or treatment advice. Clinical data cited here is sourced from published peer-reviewed trials and FDA labels. Consult a qualified healthcare professional before making any decisions about medications or research compounds. PeptiDex is an informational resource and does not sell pharmaceutical products.