Ibutamoren (MK-677)

Human clinical Growth Hormone 2 sources

Ibutamoren (MK-677) is an orally active, non-peptide growth hormone secretagogue that mimics the action of ghrelin. Research shows it can significantly increase levels of growth hormone (GH) and insulin-like growth factor 1 (IGF-1) without affecting cortisol levels, making it a subject of interest for muscle wasting, bone density, and anti-aging.

01Dosing reference

Amount

10-25 mg/day

Frequency

Once daily

Cycle

8-16 weeks on, 4 weeks off

Reference figures, not a recommendationThese values reflect amounts described in the literature and vendor documentation this database indexes. Use the reconstitution calculator to convert them into syringe units.

02Mechanism of action

Ghrelin receptor agonism

Binds to and activates the ghrelin receptor (GHSR-1a) in the brain.

GH and IGF-1 secretion

Stimulates the pituitary gland and hypothalamus to release growth hormone, which in turn increases IGF-1 production in the liver.

Anabolic and metabolic effects

Elevated GH and IGF-1 promote muscle protein synthesis, bone turnover, and lipolysis, offering potential benefits for frailty and muscle wasting.

03Human evidence

Increased lean body mass and basal metabolic rate.

A 2-month study in healthy older adults showed increased GH/IGF-1 and lean mass, though with transient increases in fasting blood glucose.

Reversal of diet-induced nitrogen wasting.

A short-term study in healthy young adults demonstrated that MK-677 reversed nitrogen wasting during caloric restriction.

04Preclinical evidence

Increased bone mineral density.

Animal models showed enhanced bone formation and density, suggesting potential for osteoporosis treatment.

Neuroprotective effects.

Mouse models indicated potential benefits in neurogenesis and spatial memory, likely mediated by IGF-1.

05What is known vs. unknown

Reasonably established

Orally bioavailable, unlike many peptide GH secretagogues.
Increases GH and IGF-1 levels sustainably over 24 hours with a single dose.
Does not significantly elevate cortisol or prolactin levels.
Can increase appetite due to its ghrelin-mimetic action.

Unknowns & limits

Long-term safety regarding insulin resistance and blood glucose elevation remains a concern.
The impact on cancer risk due to sustained elevated IGF-1 is not fully understood.

06Safety & regulatory context

Regulatory statusMK-677 is generally well-tolerated in clinical trials, but common side effects include increased appetite, mild lower extremity edema, muscle pain, and transient increases in fasting blood glucose. It is not FDA-approved for any medical condition and is classified as an investigational new drug. It is also banned by WADA in sports.

07Compared with Ipamorelin

Ibutamoren (MK-677) vs. Ipamorelin

Key difference

MK-677 is an oral non-peptide ghrelin mimetic with a long half-life (24 hours), whereas Ipamorelin is an injectable peptide with a short half-life.

When researchers discuss each

MK-677 is discussed for sustained, round-the-clock GH elevation and oral convenience, while Ipamorelin is preferred for targeted, pulsatile GH release with less appetite stimulation.

08Glossary

Secretagogue

A substance that causes another substance to be secreted.

Ghrelin

A hormone produced in the stomach that stimulates appetite and GH release.

IGF-1

Insulin-like Growth Factor 1, a hormone that manages the effects of growth hormone in the body.

09Knowledge check

Q1What is the primary mechanism of action for Ibutamoren (MK-677)?

Q2Which of the following is a common side effect associated with MK-677 in clinical studies?

Q3Which limitation about MK-677's long-term clinical effects is explicitly noted in the dossier?

Q4When researchers compare MK-677 with the peptide Ipamorelin, which stated contrast does the dossier emphasize?

Q5Which regulatory or safety statement about MK-677 is supported by the dossier?

10Sources

More in Growth Hormone

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Sermorelin

Growth Hormone

FDA-approved context

Sermorelin is a synthetic peptide consisting of the first 29 amino acids of naturally occurring growth hormone-releasing hormone (GHRH). It stimulates the pituitary gland to naturally produce and release human growth hormone (hGH), making it a subject of research for age-related growth hormone decline, body composition, and vitality.

200-500 mcg/day

Tesamorelin

Growth Hormone

FDA-approved context

Tesamorelin is a synthetic analogue of growth hormone-releasing hormone (GHRH) that stimulates the pituitary gland to secrete growth hormone. It is FDA-approved for reducing excess visceral abdominal fat in HIV-infected patients with lipodystrophy and is being researched for potential cognitive benefits.

2 mg/day

Hexarelin

Growth Hormone

Human clinical

Hexarelin is a potent, synthetic hexapeptide and growth hormone secretagogue (GHS) that stimulates the release of growth hormone. Research indicates it is one of the strongest GH-releasing peptides available, offering potential benefits for muscle growth, fat loss, and cardiovascular health without significantly increasing appetite.

100-200 mcg per dose

Research and educational use onlyNothing on this site is medical advice, a prescription, or a recommendation for human use. Compounds documented here are research chemicals. Consult a qualified clinician before making any health decision.