What it is
MK-677 (ibutamoren) is a non-peptide, orally active growth hormone secretagogue. It is the one compound in the Pantheon catalogue taken as a capsule rather than an injection, and one of the few with year-long human trial data behind it.
Mechanism of action
MK-677 binds the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus, which raises pulsatile growth hormone release and, downstream, circulating IGF-1. Because it is taken by mouth and acts for most of a day, one daily capsule holds GH and IGF-1 in the upper part of the normal range.
Evidence summary
In healthy older adults, a year of daily MK-677 raised GH and IGF-1 to young-adult levels and added about 1.1 kg of fat-free mass, with no strength gain and no change in visceral fat (Nass 2008). Shorter human studies showed improved sleep depth (Copinschi 1997), reversal of diet-induced muscle breakdown (Murphy 1998), higher bone-turnover markers (Murphy 2001) and a rise in GH secretion in obese adults (Svensson 1998). The trade-offs in the same trials were a larger appetite, some water retention and a small rise in fasting glucose.
Pantheon dosing guide
- Application
- Oral.
- BAC Water
- NA
- Dose
- 1 to 2 capsules.
- Frequency & Cycle Length
- Daily. 5 weeks to 10 weeks depending on dosing.
- Timing
- Take on an empty stomach.
- Key Benefits
- Stimulates natural growth hormone and IGF-1 release. Promotes muscle growth and strength. Boosts bone density and joint health. Improves recovery. Improves sleep quality.
Side effects
- A bigger appetite and some water retention are the effects people notice first
- Numbness or tingling is occasionally reported; in the year-long human trial the recorded effects were mild swelling in the lower legs and muscle aches, not nerve symptoms (Nass 2008)
- Fasting glucose rose slightly and insulin sensitivity fell over a year of daily use, so run it with a stopping point in view and check glucose on longer runs
- Long-term safety beyond one year has not been studied
Cited studies
- Nass R, Pezzoli SS, Oliveri MC, et al. (2008). Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Annals of Internal Medicine.PMID 18981485Read source ↗
- Copinschi G, Leproult R, Van Onderbergen A, et al. (1997). Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man. Neuroendocrinology.PMID 9349662Read source ↗
- Murphy MG, Plunkett LM, Gertz BJ, et al. (1998). MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. Journal of Clinical Endocrinology & Metabolism.PMID 9467534Read source ↗
- Murphy MG, Weiss S, McClung M, et al. (2001). Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women. Journal of Clinical Endocrinology & Metabolism.PMID 11238495Read source ↗
- Svensson J, Lönn L, Jansson JO, et al. (1998). Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure. Journal of Clinical Endocrinology & Metabolism.PMID 9467542Read source ↗
- Chapman IM, Bach MA, Van Cauter E, et al. (1996). 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. Journal of Clinical Endocrinology & Metabolism.PMID 8954023Read source ↗
Content is provided for research and educational purposes only. Products are intended solely for laboratory research and are not for human use. Nothing on this page constitutes medical advice.