Overview
MK-677 is classified as a gh secretagogue (oral) peptide. Sustained GH/IGF-1 elevation, muscle growth, improved sleep, bone density, oral dosing convenience.
Non-peptide ghrelin receptor (GHSR1a) agonist that stimulates prolonged, pulsatile growth hormone release from the pituitary gland. Unlike injectable GH peptides, MK-677 is orally bioavailable with a ~24-hour half-life, enabling once-daily dosing. Increases IGF-1 levels for up to 12 months without desensitization of the GH axis. Does not suppress natural GH secretion patterns or affect cortisol levels at standard doses.
Also known as: Ibutamoren, Ibutamoren Mesylate, L-163,191, Nutrobal
Category
GH Secretagogue (Oral)
Half-Life
24h
Route
Oral
FDA Status
Not Approved
How Does MK-677 Work?
Non-peptide ghrelin receptor (GHSR1a) agonist that stimulates prolonged, pulsatile growth hormone release from the pituitary gland. Unlike injectable GH peptides, MK-677 is orally bioavailable with a ~24-hour half-life, enabling once-daily dosing. Increases IGF-1 levels for up to 12 months without desensitization of the GH axis. Does not suppress natural GH secretion patterns or affect cortisol levels at standard doses.
At the molecular level, MK-677 operates through pathways characteristic of the GH Secretagogue (Oral) class, interacting with target receptors and downstream signaling cascades to produce its observed effects.
Published Research
The following studies are indexed from PubMed and peer-reviewed journals:
[1]MK-677 increases GH and IGF-1 without altering cortisol in healthy elderly
Chapman et al. (J. Clin. Endocrinol. Metab.): 25mg daily MK-677 for 2 weeks in healthy elderly subjects restored IGF-1 and GH profiles to young adult levels without altering cortisol, prolactin, insulin, or thyroid hormones.
Evidence: moderate[2]MK-677 2-year study: sustained IGF-1 elevation and body composition effects
Nass et al. (J. Clin. Endocrinol. Metab.): 2-year RCT in 65 healthy elderly adults. 25mg/day MK-677 increased GH and IGF-1 to young adult levels, increased fat-free mass by ~1.1kg, and did not affect BMD. Notable: fasting glucose increased by ~0.3 mmol/L.
Evidence: strong[3]MK-677 increases fat-free mass in healthy obese males
Svensson et al. (J. Clin. Endocrinol. Metab.): 8-week RCT in obese males. 25mg/day MK-677 significantly increased GH secretion, IGF-1, and fat-free mass. Transient increase in appetite and mild insulin resistance noted.
Evidence: moderate[4]MK-677 reverses diet-induced nitrogen wasting
Murphy et al. (J. Clin. Endocrinol. Metab.): MK-677 reversed diet-induced nitrogen wasting in healthy young volunteers on caloric restriction, demonstrating potent anti-catabolic properties.
Evidence: moderate[5]MK-677 improves sleep quality in healthy young and elderly
Copinschi et al. (Neuroendocrinology): MK-677 increased duration of stage IV (deep) sleep by 50% and REM sleep by 20% in both young and older subjects, correlating with enhanced overnight GH secretion.
Evidence: moderate[6]MK-677 increases bone turnover markers in postmenopausal women
Murphy et al. (J. Clin. Endocrinol. Metab.): 12-month study in postmenopausal women showing MK-677 (25mg/day) increased osteocalcin and bone-specific alkaline phosphatase, suggesting improved bone formation.
Evidence: moderate[7]Orally active growth hormone secretagogues: state of the art and clinical perspectives.
A study published in Annals of medicine investigating the effects and mechanisms.
Evidence: moderate[8]Growth hormone-releasing hormone and growth hormone-releasing peptide as therapeutic agents to enhance growth hormone secretion in disease and aging.
A study published in Recent progress in hormone research investigating the effects and mechanisms.
Evidence: preclinical[9]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.
A study published in The Journal of clinical endocrinology and metabolism investigating the effects and mechanisms.
Evidence: preclinical[10]Growth hormone-releasing peptides and the cardiovascular system.
A study published in Annales d'endocrinologie investigating the effects and mechanisms.
Evidence: preclinical[11]Nonpeptide and peptide growth hormone secretagogues act both as ghrelin receptor agonist and as positive or negative allosteric modulators of ghrelin signaling.
A study published in Molecular endocrinology (Baltimore, Md.) investigating the effects and mechanisms.
Evidence: preclinical[12]Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial.
A study published in Annals of internal medicine investigating the effects and mechanisms.
Evidence: moderate[13]Oral administration of growth hormone (GH) releasing peptide-mimetic MK-677 stimulates the GH/insulin-like growth factor-I axis in selected GH-deficient adults.
A study published in The Journal of clinical endocrinology and metabolism investigating the effects and mechanisms.
Evidence: preclinical[14]Two-month treatment of obese subjects with the oral growth hormone (GH) secretagogue MK-677 increases GH secretion, fat-free mass, and energy expenditure.
A study published in The Journal of clinical endocrinology and metabolism investigating the effects and mechanisms.
Evidence: preclinical[15]Discrepancy between serum leptin values and total body fat in response to the oral growth hormone secretagogue MK-677.
A study published in Clinical endocrinology investigating the effects and mechanisms.
Evidence: preclinical[16]Effects of a 7-day treatment with a novel, orally active, growth hormone (GH) secretagogue, MK-677, on 24-hour GH profiles, insulin-like growth factor I, and adrenocortical function in normal young men.
A study published in The Journal of clinical endocrinology and metabolism investigating the effects and mechanisms.
Evidence: preclinical[17]Treatment with the oral growth hormone secretagogue MK-677 increases markers of bone formation and bone resorption in obese young males.
A study published in Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research investigating the effects and mechanisms.
Evidence: preclinical[18]Brain and kidney GHS-R1a underexpression is associated with changes in renal function and hemodynamics during neurogenic hypertension.
A study published in Molecular and cellular endocrinology investigating the effects and mechanisms.
Evidence: preclinical[19]Prolonged oral treatment with MK-677, a novel growth hormone secretagogue, improves sleep quality in man.
A study published in Neuroendocrinology investigating the effects and mechanisms.
Evidence: preclinical[20]Pharmacological profile of a new orally active growth hormone secretagogue, SM-130686.
A study published in The Journal of endocrinology investigating the effects and mechanisms.
Evidence: preclinicalSafety Profile
Oral GH secretagogue with extensive clinical data (2+ year RCTs). Key concern: impairs insulin sensitivity and raises fasting glucose, especially in elderly/obese populations. One hip fracture trial in elderly was stopped early due to CHF signals. WADA prohibited. Not FDA-approved. Use caution in pre-diabetic or insulin-resistant individuals.
| Side Effect | Incidence | Severity |
|---|---|---|
| Increased appetite | ~40-60% of users | moderate |
| Water retention / bloating | ~30% of users | moderate |
| Insulin resistance / elevated fasting glucose | ~15-25% of users | moderate |
| Lethargy / drowsiness | ~15% of users | mild |
| Numbness / tingling (paresthesia) | ~8% of users | mild |
| Joint pain | ~5% of users | mild |
Sourcing MK-677 for Research
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Full Research Profile
MK-677 — dosing, interactions, timelines & more
Comprehensive compound profile with sourcing information, stacking synergies, and outcome timelines.