MK-677
Ibutamoren — GH Secretagogue
What is MK-677?
MK-677 (Ibutamoren) is a non-peptide growth hormone secretagogue that mimics ghrelin by binding to GHS-R1a receptors in the pituitary and hypothalamus. Unlike injectable GHRPs, it is orally bioavailable with a half-life of approximately 24 hours — allowing once-daily oral dosing.
MK-677 stimulates GH and IGF-1 release through the ghrelin receptor pathway without affecting cortisol, prolactin, or other pituitary hormones at standard doses. It produces a sustained elevation in GH pulse amplitude throughout the day.
Research Evidence
Multiple clinical trials in elderly and GH-deficient patients show consistent IGF-1 elevation of 40-60% at 25mg/day. Effects are dose-dependent and sustained with continued use.
Studies in elderly populations demonstrate improvements in lean body mass, bone mineral density, and functional measures over 12-24 month protocols.
MK-677 increases slow-wave sleep duration, which correlates with the natural GH peak. Improved sleep is consistently self-reported in community protocols.
Evidence grades: Gold = RCT human data · Silver = multiple animal studies, consistent · Bronze = limited or preliminary
Dosing Protocols
Reconstitution Guide
This compound does not require reconstitution — it is taken orally and does not require preparation.
Frequently Asked Questions
Does MK-677 suppress testosterone?
No. MK-677 acts through the ghrelin receptor and does not affect the HPT axis. It does not suppress testosterone and does not require post-cycle therapy.
What are the main side effects of MK-677?
The most common are increased appetite, water retention in the first 2-4 weeks, and fatigue at higher doses. These are dose-dependent and typically resolve with dose reduction. Transient insulin resistance has been observed at 25mg in clinical studies.
References
- [1]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;81(12):4249-4257.
- [2]Nass R, Pezzoli SS, Oliveri MC, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults. Ann Intern Med. 2008;149(9):601-611.
This profile was prepared using AI-assisted research synthesis. Citations are provided where applicable — verify with primary sources before clinical application.
Share this article