MK-677 dosage protocol

What the compound is

MK-677, also known as ibutamoren mesilate, is an orally active, non-peptide growth hormone secretagogue (GHS) (PMID 9467534, PMID 35716382, PMID 36354265). It is a mimic of growth hormone-releasing peptide (PMID 9467534). MK-677 binds to the ghrelin receptor, stimulating the secretion of endogenous growth hormone (GH) (PMID 36354265). It is considered a potent, long-acting, selective GHS (PMID 35716382).

MK-677 is an emerging peptide supplement that is often perceived as low risk by patients and athletes (PMID 42578445). It is one of the prevalent performance-enhancing compounds available online and has potential for abuse in both human and equine sports (PMID 36354265).

How it is thought to work

MK-677 stimulates the secretion of endogenous growth hormone (GH) by binding to the ghrelin receptor (PMID 36354265). In a human study, 25 mg of oral MK-677 once daily for seven days produced a peak GH response of 22.6 ± 9.3 micrograms/L, compared to approximately 7 micrograms/L with placebo (PMID 9467534).

This compound also significantly increased insulin-like growth factor-I (IGF-I) concentrations, from 186 ± 19 ng/mL to 264 ± 31 ng/mL after seven days of treatment, in human volunteers (PMID 9467534). IGF-I is a hormone that mediates the effects of growth hormone. IGF binding protein-3 also significantly increased with MK-677 treatment in humans (PMID 9467534).

What laboratory and animal studies report

In animal models, typically rats, MK-677 and other compounds demonstrated unique mechanisms with promising but variable effects on tendon, muscle, bone, and ligament healing (PMID 42578445).

Studies in thoroughbred horses identified 22 metabolites of ibutamoren after oral administration, including hydroxylated, dissociated side chains, and hydrogenated metabolites (PMID 35716382). MK-677 and its O-dealkylated metabolite were detectable in equine hair for extended periods, up to 209 days in mane and 358 days in tail, following oral administration (PMID 36354265).

Human evidence so far

In a human double-blind, randomized, placebo-controlled study with eight healthy volunteers, oral MK-677 (25 mg daily) reversed diet-induced protein catabolism (the breakdown of protein) (PMID 9467534). Participants receiving MK-677 had a mean daily nitrogen balance of 0.31 ± 0.21 g/day, compared to -1.48 ± 0.21 g/day in the placebo group, indicating improved protein retention (PMID 9467534).

A systematic review noted that human clinical studies on emerging peptides like MK-677 are limited, often lacking robust controls or rigorous study designs (PMID 42578445). These human data showed modest improvements at best for metabolic bone health and degenerative knee pain (PMID 42578445).

A case report of a 25-year-old male co-administering LGD-4033 and MK-677 (15 mg daily for 5 weeks) showed increases in body mass, lean mass, and fat mass (PMID 36303408). However, it also negatively impacted bone mineral content and density, serum lipids (cholesterol, triglycerides, LDL, HDL), liver enzymes (AST, ALT), and androgen-associated biomarkers (free testosterone, total testosterone, SHBG) (PMID 36303408). All affected variables, except total fat mass, returned to pre-cycle values after cessation (PMID 36303408).

MK-677 has been associated with significant risks, including congestive heart failure and metabolic dysfunction such as insulin resistance (PMID 42578445). A case of hepatotoxicity (liver injury) was reported in an otherwise healthy man who developed transaminitis (elevated liver enzymes) after two months of MK-677 use, which resolved after stopping the supplement (PMID 40675653).

Open questions and limitations

Despite promising findings in animal studies, the claimed benefits of emerging peptide supplements like MK-677 for musculoskeletal recovery and performance remain largely unsubstantiated by current human trials (PMID 42578445). There is significant heterogeneity in dosing and routes of administration across studies (PMID 42578445).

While MK-677 can be detected in human hair, more data on expected concentrations after single exposure versus a doping regimen are needed for precise interpretation of hair test results (PMID 40882886).

Key terms explained

<b>Growth hormone secretagogue (GHS)</b>: A substance that stimulates the secretion of growth hormone.

<b>Ghrelin receptor</b>: A receptor in the body that, when activated, can stimulate growth hormone release.

<b>Endogenous growth hormone</b>: Growth hormone naturally produced by the body.

<b>Nitrogen balance</b>: The difference between the amount of nitrogen (from protein) consumed and the amount excreted; a positive balance suggests protein retention, while a negative balance suggests protein breakdown.

<b>Catabolism</b>: The breakdown of complex molecules in living organisms to form simpler ones, often releasing energy.

<b>Insulin-like growth factor-I (IGF-I)</b>: A hormone that mediates many of the growth-promoting effects of growth hormone.

<b>Transaminitis</b>: Elevated levels of liver enzymes (like AST and ALT) in the blood, indicating liver cell damage.

<b>Hepatotoxicity</b>: Liver damage caused by chemical substances.