MK-677 Evidence Guide
MK-677 has genuine Phase 2 human data on GH/IGF-1 elevation, body composition, and sleep quality across multiple independent groups - more human evidence than most GH secretagogues in this library. It is oral, which meaningfully differentiates it. The trade-off is water retention, increased appetite, and insulin resistance at sustained doses. For researchers interested in GH axis stimulation with an oral route, MK-677 is the best-evidenced option available.
Our Take
MK-677 has genuine Phase 2 human data on GH/IGF-1 elevation, body composition, and sleep quality across multiple independent groups - more human evidence than most GH secretagogues in this library. It is oral, which meaningfully differentiates it. The trade-off is water retention, increased appetite, and insulin resistance at sustained doses. For researchers interested in GH axis stimulation with an oral route, MK-677 is the best-evidenced option available.
- Best for
- GH/IGF-1 elevation, body composition research, sleep architecture, GH deficiency investigation
- Evidence grade
- Level B
- Confidence
- Moderate
- Starting point
- 25mg oral, once daily (evening dosing to align with GH pulse)
Benefits and Evidence
- Growth Hormone and IGF-1 Elevation: Level B, includes human evidence - Consistently increases GH and IGF-1 levels to youthful ranges in elderly and GH-deficient populations, with effects sustained over months of treatment.
- Lean Body Mass: Level B, includes human evidence - Modest increases in fat-free mass observed in clinical trials, particularly in elderly and sarcopenic populations over 12 months of treatment.
- Sleep Quality: Level B, includes human evidence - Improved sleep quality with increased Stage IV (deep) sleep duration and REM sleep observed in healthy young and elderly subjects.
- Appetite Increase: Level B, includes human evidence - Significant appetite stimulation due to ghrelin receptor activation, which can be problematic for weight management but beneficial in cachexia or sarcopenia.
Side Effects and Warnings
- Increased appetite
- Water retention and edema
- Muscle pain
- Joint pain
- Elevated fasting blood glucose
- Lethargy
- Numbness and tingling in extremities
- Not FDA approved - investigational compound
Research Dosage References
- <strong>Oral</strong> - 25 mg - Once daily - Most commonly studied dose. Taken before bed to align with natural GH release patterns and minimize daytime appetite stimulation.
- <strong>Oral</strong> - 10 mg - Once daily - Lower dose used in some studies, still effective at raising IGF-1 but with fewer side effects.
Mechanism of Action
MK-677 acts as a ghrelin mimetic, binding to and activating the growth hormone secretagogue receptor type 1a (GHSR1a) in the hypothalamus and pituitary gland. This triggers growth hormone release through a mechanism distinct from GHRH, operating through the ghrelin/GHSR pathway. Activation of GHSR1a by MK-677 stimulates GH release in a pulsatile manner that preserves the natural circadian rhythm of GH secretion. The compound amplifies GH pulse amplitude without significantly affecting pulse frequency, resulting in elevated 24-hour GH profiles similar to those seen in younger individuals. The sustained elevation in GH levels leads to increased hepatic production of IGF-1, which mediates many of the anabolic and metabolic effects attributed to the GH/IGF-1 axis. Importantly, MK-677 does not suppress the hypothalamic-pituitary-adrenal axis, and cortisol levels remain largely unchanged. As a ghrelin mimetic, MK-677 also stimulates appetite through hypothalamic orexigenic pathways, which can be both a therapeutic benefit (in catabolic conditions) and a limitation (in obesity management).
Legal Status
Not FDA approved. Not a scheduled substance in most countries. Available as a research chemical. Banned by WADA in competitive sports.
Primary Sources
- MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism. Journal of Clinical Endocrinology & Metabolism, 1998.
- Two-year effects of ibutamoren on muscle wasting and growth hormone levels in elderly adults. Journal of Clinical Endocrinology & Metabolism, 2008.
- Oral administration of growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adults. Journal of Bone and Mineral Research, 1999.