📚 Wiki Growth Hormone MK-677

MK-677

◎ Phase II (discontinued by Merck)
MK-677 (Ibutamoren), Oral Growth Hormone Secretagogue
Also known as: Ibutamoren, Ibutamoren mesylate, MK677, L-163,191
Brand names: Nutrobal (research)
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Quick Summary

MK-677 (ibutamoren) is an orally active, non-peptide ghrelin receptor agonist (GHS-R1a) that stimulates GH release from the pituitary without requiring injection. It was developed by Merck and advanced through Phase II trials for growth hormone deficiency, muscle wasting, and frailty in elderly populations.

Growth Hormone & IGF Phase II (Discontinued) WADA Prohibited
MK-677 (ibutamoren) is an orally active, non-peptide ghrelin/" class="wiki-internal-link">ghrelin receptor agonist (GHS-R1a) that stimulates GH release from the pituitary without requiring injection. It was developed by Merck and advanced through Phase II trials for growth hormone deficiency, muscle wasting, and frailty in elderly populations. Its 24-hour half-life allows once-daily dosing and produces sustained elevations in GH and IGF-1. Unlike GHRP peptides, it is not a peptide itself, making it resistant to GI proteolysis and orally bioavailable.
Storage Stability
Lyophilized
~1 year
Reconstituted
N/A (oral)
Room temp
Stable (dry)

Mechanism of Action

Ghrelin Receptor Agonism (GHS-R1a)

MK-677 binds the ghrelin/" class="wiki-internal-link">ghrelin receptor (GHS-R1a) on pituitary somatotrophs, mimicking endogenous ghrelin's GH-releasing action. This stimulates GH synthesis and pulsatile secretion.

Sustained IGF-1 Elevation

Due to its 24-hour half-life, MK-677 produces sustained GH elevation that drives continuous IGF-1 production in the liver, the primary anabolic mediator.

Somatostatin Independence

GHS-R1a agonism partially bypasses somatostatin feedback that limits endogenous GH pulsatility, producing higher GH area-under-the-curve than natural secretion.

Research Summary

Phase II, Muscle Wasting

In cachexia/muscle wasting patients, MK-677 25 mg/day for 8 weeks significantly increased lean mass (~2.7 kg) and GH/IGF-1 levels. Effect persisted for duration of treatment.

Elderly Frailty

In adults 60–81 years old, MK-677 25 mg/day for 24 months increased muscle mass and strength and reduced falls frequency, without increasing fractures or cardiovascular events.

GH Deficiency

Children with GHD showed increased growth velocity with MK-677, comparable to injectable GH, demonstrating the pituitary's preserved capacity when properly stimulated.

Side Effects

Water retention, increased appetite, and transient insulin resistance at higher doses. Cortisol and prolactin may mildly increase.

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Research Protocols

Dosing

10–25 mg orally once daily. Most research protocols use 25 mg. Taking before bed reduces the GH pulse during sleep (natural peak amplification).

Cycle

8–12 weeks. Some researchers use longer term; insulin sensitivity monitoring recommended for extended use.

Water Retention Management

Moderate sodium restriction reduces the edema/water retention common in the first 2–4 weeks, which resolves with continued use.

Storage & Handling

MK-677 is typically supplied as capsules or tablets (non-peptide). Store at room temperature, dry, away from light and moisture. Shelf life 2–3 years properly stored.


References

  • [1]Copinschi G, et al. "MK-677 administered orally stimulates GH secretion." J Clin Endocrinol Metab, 1996.
  • [2]Chapman IM, et al. "Stimulation of the GH/IGF-1 axis by daily oral MK-677 in elderly adults." J Clin Endocrinol Metab, 1996.
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Verified Scientific Data Last audited:
Data Sources & External References
CAS Registry: 159752-10-0  ·  Molecular Formula: C27H36N4O5S  ·  Source: peer-reviewed literature  ·  Domain: ascendpeptide.org
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