MK-677 (Ibutamoren)
MK-0677, Oral growth hormone secretagogue (NOT a SARM)
Evidence grade 2 of 5, Thin. Read how the Atlas grades evidence.
The written rationale for this grade is still being prepared.
- FDA
- Not FDA approved; multiple Phase II trials, never submitted for approval
- WADA
- Prohibited at all times (S2, Growth Hormone Secretagogues)
Reference only. Not medical advice.
What can go wrong
Increased fasting blood glucose and worsened insulin sensitivity (relevant for prediabetes/diabetes); fluid retention and edema; arthralgia; increased appetite; possible increases in blood pressure and, with chronic GH/IGF-1 elevation, theoretical concern about IGF-1-driven growth. Consumer products are unregulated and frequently mislabeled. Prohibited in WADA sport.
This is something to take to a clinician. The Atlas can tell you what is known about mk-677 (ibutamoren) in general. It cannot tell you what is happening in your body, and the difference matters most for exactly the symptoms that bring people to this page.
MK-677 (ibutamoren, MK-0677) is an orally active, non-peptide growth hormone secretagogue developed by Merck in the 1990s. It mimics ghrelin at the GHS-R1a receptor to stimulate GH and IGF-1 release. It is not a SARM and has no androgenic mechanism, but is sold alongside them. Merck ran multiple Phase II trials and never sought approval; documented issues include increased fasting glucose, worsened insulin sensitivity, water retention/edema, and increased appetite.
Sold with SARMs, but it is a GH secretagogue, and it raises blood sugar and causes edema.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
How it is supposed to work
Ibutamoren is a non-peptidyl agonist of the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus, driving pulsatile release of growth hormone and downstream IGF-1. It does not act on the androgen receptor and does not directly build muscle via an anabolic-androgen pathway, its category placement alongside SARMs is a marketing convention, not pharmacology.
Modest lean mass, real metabolic cost
In a 12-month randomized trial in older adults, MK-677 raised fat-free mass by roughly 1 kg but did not improve strength or function and worsened insulin sensitivity. Raising GH/IGF-1 chronically also drives fluid retention (edema, arthralgia) and higher fasting glucose. Merck's discontinuation reflected a modest efficacy-to-liability balance, not a clean profile.
Safety in detail
MK-677 chronically raises GH and IGF-1 and can worsen glucose control and cause edema. It is an unapproved drug (not a SARM and not a supplement). Self-administration without medical oversight carries documented metabolic and fluid-balance risks.
Replacement is not the same as a cycle
By design it pushes GH/IGF-1 above baseline. Sustained supraphysiological GH/IGF-1 signaling is the source of its insulin-resistance and edema risks; higher/longer consumer dosing amplifies these.
What it does to fertility
MK-677 does not directly suppress the HPT axis the way SARMs do; it is a GH secretagogue. Its principal risks are metabolic (glucose, fluid) rather than gonadal.
What has to be monitored
The bloodwork this needs, and the reason it belongs with a clinician rather than a website.
- Fasting glucose / HbA1c / insulin sensitivity
- IGF-1 levels
- Blood pressure and signs of edema
- Thyroid function (as clinically indicated)
What people get wrong
Often saidMK-677 is a SARM
ActuallyIt is a ghrelin-receptor agonist / GH secretagogue with no androgenic mechanism.
Often saidIt is a safe way to raise GH
ActuallyIn controlled trials it raised fasting glucose, worsened insulin sensitivity and caused edema, and Merck never brought it to approval.
Who profits, and who pushes back
Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.
How we got here
MK-677 (MK-0677) was developed by Merck in the 1990s as an orally active successor to injectable GH secretagogues, aiming at GH deficiency, frailty and osteoporosis. It cleared multiple Phase II trials but was never submitted for approval, body-composition changes were statistically real but clinically modest, and metabolic liabilities were evident. It later became a staple of the gray-market 'SARM' trade despite not being a SARM.
- 1990sMerck develops MK-0677 as an oral GH secretagogue
- 200812-month older-adult trial shows modest lean mass, worse insulin sensitivity
- 2010sSold widely online alongside SARMs as 'MK-677'
At a glance
- Developer
- Merck Research Laboratories
- Code
- MK-0677 / ibutamoren
- Class
- Ghrelin-receptor (GHS-R1a) agonist
- FDA approvals
- None
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about MK-677 (Ibutamoren). A short entry is not a safe entry.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
Sources
The studies below are named and described, but not linked. You cannot open them from here and check our reading against them, which means this page is our summary of the literature rather than a document you can verify. Weigh it accordingly until the links exist.
The studies that matter
Nass et al., 12-month MK-677 in older adults (Ann Intern Med)2008
Increased fat-free mass ~1.1 kg; did not improve strength; adverse effects on glucose/insulin sensitivity
Murphy et al. / Merck Phase II GH-secretagogue trials1990s-2000s
Raised GH/IGF-1; effects on body composition modest; edema and glucose effects noted