MK-677 (Capsule) (S2)

MK-677 (Ibutamoren)

The only oral GH secretagogue — stimulates GH and IGF-1 through ghrelin receptor activation.

Prohibited in competition. This compound is on the WADA Prohibited List (class [S0 / S2.3 / S2]), banned at all times, both in and out of competition. Athletes subject to WADA or USADA testing should not use it.

100% 50% · t½ Time → Serum level
Molecular Weight Not specified
Half-Life Varies
Typical Dose One capsule per prescriber guidance
Cycle Length 8–16 weeks

Description

MK-677 (Ibutamoren, also known as L-163,191) is a non-peptide oral growth hormone secretagogue that mimics the action of ghrelin and activates the GHS-R1a (growth hormone secretagogue receptor 1a). It is the only orally bioavailable GH secretagogue, providing a convenient alternative to injectable GHRPs (growth hormone releasing peptides) such as GHRP-2 and GHRP-6. MK-677 was developed by Merck and has been evaluated in multiple Phase II human clinical trials for conditions including GH deficiency, muscle wasting, hip fracture recovery, and Alzheimer’s disease. It significantly elevates both pulsatile GH secretion and IGF-1 levels, with effects lasting approximately 24 hours from a single dose. Unlike injectable GH, MK-677 stimulates the body’s own GH production in a physiological pulsatile pattern, which is considered safer and more natural than exogenous GH administration. The compound has demonstrated improvements in body composition, bone mineral density, and sleep quality in human studies.

Key Characteristics

Molecular Formula

Molecular Weight

Half-Life

Administration Routes

Oral capsule

Typical Dose

One capsule (per prescriber guidance)

Frequency

Once daily (bedtime)

Investigated Benefits

* Benefits based on preclinical/animal research unless otherwise noted.

Mechanism of Action

“The only oral GH secretagogue — stimulates GH and IGF-1 through ghrelin receptor activation.”

MK-677 binds to and activates the ghrelin receptor (GHS-R1a) in the pituitary gland and hypothalamus, mimicking the action of the endogenous hunger hormone ghrelin. This activation stimulates the pituitary to release GH in pulsatile bursts, which in turn stimulates the liver to produce IGF-1 (insulin-like growth factor 1). Unlike synthetic GH, MK-677 preserves the natural pulsatile pattern of GH secretion, which is important for maintaining GH receptor sensitivity and avoiding the desensitization that can occur with continuous GH exposure. MK-677 has a half-life of approximately 24 hours, allowing for once-daily dosing. Bedtime administration aligns with the natural nocturnal GH pulse and may enhance sleep quality through GH’s effects on slow-wave sleep architecture. The compound also increases ghrelin signaling in the hypothalamus, which stimulates appetite — a common and expected effect that should be managed through dietary awareness.

Administration Routes

Oral capsule

Key Characteristics

Typical Dose

One capsule (per prescriber guidance)

Frequency

Once daily (bedtime)

Cycle Length

8–16 weeks

Administration

Oral capsule

Protocol Notes

Bedtime dosing aligns with natural GH pulse. Start with 10 mg to assess tolerance. Increased hunger is common — manage caloric intake. Monitor IGF-1 every 3 months.

Reconstitution Guide

Storage Information

Store at room temperature, away from light and moisture.

Quality & Sourcing Standards

When sourcing MK-677 (Capsule) for research purposes, the following quality benchmarks should be verified before use.

Purity:

>98% (verified by HPLC)

Certificate of Analysis (COA):

Must be provided by supplier

Endotoxin Testing:

<0.1 EU/mg (prevents bacterial contamination)

GMP Compliance:

Manufactured in cGMP-certified facility

Third-Party Testing:

Independent lab verification preferred

Storage Information

Store at room temperature, away from light and moisture.

FDA Disclaimer

The statements made within this website have not been evaluated by the US Food and Drug Administration. The products and information provided are not intended to diagnose, treat, cure, or prevent any disease. This website is intended for educational and research purposes only. Many peptides described on this site are not approved by the FDA for human therapeutic use and are classified as research chemicals. Nothing on this site constitutes medical advice.

Research Highlights

1

Demonstrated significant GH and IGF-1 elevation in human Phase II trials

2

Improved body composition in elderly patients

3

Increased bone mineral density in Phase II trials

Evidence Level

Multiple animal studies and/or early human trials. Reasonable confidence in mechanism, but human data is limited.

Compatible Peptides

Peptides commonly used alongside Sermorelin (Capsule) for synergistic effects.

Ipamorelin

The most selective GHRP available, stimulating GH release with minimal cortisol or prolactin elevation.

BPC-157 (Capsule)

Oral BPC-157 for gastrointestinal healing, gut permeability, and systemic anti-inflammatory effects.

Quick Reference

Category

Hormone & GH

Status

Research Only
 

Dose

One capsule (per prescriber guidance)

Frequency

Once daily (bedtime)

Cycle

8–16 weeks