MK-677, also known as ibutamoren, is often called a „growth hormone pill“ in fitness communities. Forums describe it as a safe alternative to injections. Clinical studies paint a more cautious picture, though: some measurements change noticeably, but with real risks and no evidence of greater strength or performance. In this article we sum up what human research tells us about ibutamoren, its side effects, and its status in sport and law.
What is MK-677 (ibutamoren)?
Ibutamoren is a synthetic compound developed by the pharmaceutical company Merck in the 1990s. It is neither a hormone nor a peptide, even though it is often sold alongside peptides. It is a small molecule taken by mouth that mimics ghrelin, the hormone your body releases when you are hungry. It binds to the ghrelin receptor in the brain, and the pituitary gland then releases more growth hormone (GH). This is followed by higher levels of IGF-1, a growth factor made mainly by the liver.
The compound was originally studied as a possible treatment for older people, patients recovering from fractures and people with growth hormone deficiency. None of this research led to approval. Today ibutamoren is not a licensed medicine in either the EU or the USA.
What human studies have shown
Two-year study in older adults (2008)
The most cited study was published by Nass and colleagues in the Annals of Internal Medicine. It involved 65 healthy people aged 60 to 81 and was double-blind and placebo-controlled. Participants took 25 mg of ibutamoren or a placebo daily for two years. The results:
- GH and IGF-1 levels rose to roughly those typical of young adults;
- lean mass increased by about 1.1 kg after one year, while it fell by about 0.5 kg in the placebo group;
- according to expert commentary, most of the gain was body water rather than new muscle tissue;
- strength and physical function did not measurably improve;
- participants felt hungrier and gained weight;
- fasting blood sugar rose by an average of 0.3 mmol/L (about 5 mg/dL), and insulin sensitivity fell.
Study in patients after hip fracture (2011)
Another clinical trial looked at whether ibutamoren helps older patients recover after a hip fracture. IGF-1 levels rose, but most of the functional measures did not improve. The trial was stopped early because several patients developed heart failure. The authors described the compound’s safety profile in these patients as unfavourable.
What is missing
There are no good-quality studies in young, healthy people who train, which is exactly the group that uses ibutamoren most. Claims of „rapid muscle growth“, fat burning or faster recovery come mainly from user experiences, not research. We also don’t know the effects of long-term use or the quality of products sold „for research purposes“.
Side effects and risks
These problems come up repeatedly in studies and reports:
- Strong hunger and weight gain: ibutamoren mimics the „hunger hormone“, so this is a direct result of how it works.
- Water retention and swelling, especially in the arms and legs.
- Higher blood sugar and lower insulin sensitivity: a risk for people with prediabetes, diabetes or excess weight.
- Joint and muscle pain, tingling in the hands (similar to having too much growth hormone).
- Heart failure in the study of older patients, which is why it was stopped early.
- Unknown product content: the US Food and Drug Administration (FDA) has repeatedly found undeclared ibutamoren in products sold as dietary supplements and warned sellers that it is an unapproved drug.
Persistently high IGF-1 levels have also been linked in research to questions about tumour growth. This has not been directly shown for ibutamoren. It is, however, one reason why doctors monitor IGF-1 regularly during growth hormone treatment. Ibutamoren bought outside a pharmacy comes with no such supervision.
MK-677 in sport and law
- Doping: the World Anti-Doping Agency (WADA) lists ibutamoren as a prohibited substance. It belongs to group S2, among substances that stimulate growth hormone release, and is banned at all times, not just in competition. A positive test leads to disciplinary proceedings for the athlete.
- Medicine: it is not licensed as a medicine in the EU or the USA.
- Dietary supplement: the FDA states that ibutamoren cannot be a dietary supplement. Labels such as „research only“ or „not for human consumption“ don’t change that.
Proven ways to support your own growth hormone
If your goal is more muscle, less fat and better recovery, these steps have much stronger evidence behind them and none of the same risks:
- Good sleep, 7 to 9 hours. Most growth hormone is released during deep sleep in the first half of the night.
- Strength training with progression, meaning gradually more weight, reps or sets.
- Enough protein: for people who train regularly, 1.6 to 2.2 g per kilogram of body weight per day is often cited.
- Less body fat. Excess fat, especially around the belly, dampens GH release.
- Creatine, the best-researched supplement for strength and muscle size.
Read more in our article on boosting growth hormone naturally.
Summary
MK-677 reliably raises growth hormone and IGF-1 levels. That does not mean more strength or better performance. In the longest study, people mainly gained water and weight, and their blood sugar got worse. Another trial was stopped because of heart failure. The compound is not approved as a medicine or a dietary supplement and is banned in sport. If you are considering it, talk to a doctor first, ideally an endocrinologist.
Sources
- Nass R. et al.: Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults. Annals of Internal Medicine, 2008. study record
- Adunsky A. et al.: MK-0677 (ibutamoren mesylate) for the treatment of patients recovering from hip fracture. Archives of Gerontology and Geriatrics, 2011. PubMed
- Commentary on the study by Nass et al., Nature Clinical Practice Gastroenterology & Hepatology. nature.com
- U.S. FDA: warning about a product with hidden ibutamoren (2025). fda.gov
- Sport Integrity Australia: Ibutamoren (MK-677), status under the WADA list. sportintegrity.gov.au
Sponsored link: This website is partnered with Peptide Revolution. The link is an advertisement, not a recommendation to use the product. The notice at the top of this article applies.
Author: Ondrej · Last updated: 14 Nov 2026
? Clinical trial results, side effects, the WADA ban and safer ways to support your own growth hormone.){kind=link}