The information on this page is compiled from peer-reviewed research and is provided for educational and research purposes only. It is not medical advice, a diagnosis, or a treatment recommendation. Peptides discussed here may not be approved for human use in your jurisdiction. Always consult a qualified healthcare provider before starting, stopping, or modifying any health protocol.
What is MK-677?
MK-677, also known as ibutamoren, is a potent, orally active, non-peptide growth hormone secretagogue that selectively mimics the action of ghrelin by binding to growth hormone secretagogue receptors (GHSR) in the brain and pituitary. Unlike injectable growth hormone-releasing peptides, MK-677 is active when taken orally and has a half-life of approximately 24 hours, allowing once-daily dosing. It is technically classified as a small molecule rather than a peptide, but it functions within the peptide growth hormone axis and is widely studied in the context of GH-elevating peptide therapies.
The mechanism of action involves four complementary pathways: stimulation of growth hormone-releasing hormone (GHRH) production, suppression of somatostatin (the hormone that inhibits GH release), amplification of GHRH signaling at the anterior pituitary, and attenuation of somatostatin receptor signaling. The result is a sustained, physiological increase in pulsatile GH secretion, which in turn drives hepatic production of insulin-like growth factor 1 (IGF-1). A key feature of this mechanism is that pulsatility of GH secretion is preserved, in contrast to exogenous GH administration, which produces non-physiological constant elevation.
Clinical research has documented the hormonal effects of MK-677 in human subjects. In a study of healthy adults receiving 25 mg orally once daily, serum IGF-1 increased by 60.1% at 6 weeks and 72.9% at 12 months [1]. GH secretion increased up to 97% above baseline in some study parameters. MK-677 also improved nitrogen balance in subjects undergoing diet-induced catabolism [3], suggesting a protein-sparing effect relevant to muscle preservation during caloric restriction. Lean body mass increased in multiple trials without corresponding changes in total fat mass or visceral fat, which distinguishes its body composition effects from those of exogenous GH.
Research has also explored MK-677 in conditions associated with GH decline, including aging-related muscle wasting, hip fracture recovery, and growth hormone deficiency. A notable two-year study in healthy older adults (60 to 81 years) found significant increases in lean body mass, GH pulse amplitude, and IGF-1, though functional strength gains were modest. MK-677 remains an investigational drug (IND) in the United States and has not received FDA approval for any indication.
Research Supply
Source high-purity MK-677 for your research
Dosage Guide
Route: Oral (capsules or tablets); no reconstitution required
Dosing Schedule
| Period | Dose |
|---|---|
| Initial or conservative dosing | 5 mg/day (lower side effect burden) |
| General GH support | 10 mg/day (frequently used in longer research protocols) |
| Clinical trial standard | 25 mg/day (used in most published human studies) |
Reconstitution
Injection Volumes
| Dose | Volume | Syringe Units |
|---|
Cycling Protocol
16-24 weeks
Variable; off periods commonly reported in research protocols
Human research protocols have ranged from 8 weeks to 24 months. Off periods are recommended due to potential insulin resistance with prolonged continuous use.
Administration Tips
- Take orally once daily; the 24-hour half-life makes single daily dosing sufficient
- Consider taking the dose at night before sleep to reduce daytime hunger from ghrelin receptor activity
- Evening dosing may coincide with the natural nocturnal GH pulse
- Monitor fasting blood glucose and HbA1c with prolonged use
- Many research protocols limit continuous cycles to 16-24 weeks followed by an off period due to cortisol elevation and potential insulin resistance
Risks & Side Effects
Commonly Reported
Serious Risks
Worsening insulin resistance
Of particular concern in pre-diabetic or diabetic individuals. Monitor fasting glucose and HbA1c throughout the research protocol.
Elevated IGF-1 beyond reference range
High sustained IGF-1 levels are theoretically associated with promotion of occult malignancies. This risk is not quantified in human studies but is a class concern with GH-axis stimulation.
Pituitary tumor growth
MK-677 is contraindicated in individuals with active pituitary or hypothalamic tumors due to potential for promoting growth.
Cardiac fluid retention
Fluid retention may exacerbate heart failure or other cardiac conditions in susceptible individuals.
Contraindications
- Active or suspected malignancy (particularly IGF-1-sensitive cancers)
- Diabetes mellitus or significant insulin resistance (without medical supervision)
- Active pituitary or hypothalamic disease
- Pregnancy or breastfeeding
- Pediatric patients with open growth plates (risk of abnormal growth)
Related Peptides
Experts Covering MK-677
LEGAL DISCLAIMER
The information provided on this page is for educational and informational purposes only and is not intended as medical advice. MK-677 (ibutamoren) has not been approved by the FDA for any medical condition and remains an investigational compound. Always consult with a qualified healthcare professional before starting any peptide therapy. Individual results may vary. Peptides Institute is not responsible for any adverse effects resulting from the use of information provided on this site.
Frequently Asked Questions
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References
- Chapman IM, Bach MA, Van Cauter E, et al.. Stimulation of the growth hormone (GH)-insulin-like growth factor I axis by daily oral administration of a GH secretogogue (MK-677) in healthy elderly subjects. J Clin Endocrinol Metab. 1996. PMID 8954023
- Nass R, Pezzoli SS, Oliveri MC, et al.. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Ann Intern Med. 2008. PMID 18981485
- Murphy MG, Plunkett LM, Gertz BJ, et al.. MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism [^3]. J Clin Endocrinol Metab. 1998. PMID 9467534
Regulatory & Official Sources
- Ibutamoren (MK-677) — Wikipedia