Ostarine (MK-2866), also known as enobosarm, is a selective androgen receptor modulator (SARM). SARMs like Ostarine stimulate steroid hormone receptors – androgen receptors – mimicking testosterone .
Scientists initially hypothesized that, unlike typical steroids, SARMs would be able to target specific tissues, such as the muscles or bones. In theory, this was supposed to limit their side effects .
Bodybuilders tend to take this unapproved theory as “proof” that they won’t have to deal with severe testosterone suppression and increased estrogens if they take SARMs. However, this is far from true.
Still, SARMs have surfaced as a popular new class of appearance and performance enhancers. People misperceive them as safer and “cleaner” due to a basic misunderstanding of the available scientific data, which is hyped in various bodybuilding blogs.
Many bodybuilders and athletes swear by Ostarine and claim it offers significant muscle mass and performance gains with few risks.
In reality, the “SARMs selectivity theory” might be completely false. It has never been proven, and SARMs like Ostarine never passed proper clinical trials. SARMs may turn out to be much more dangerous than previously thought.
To create further confusion, some researchers believe Ostarine might be safer than steroids, though they still have no data to back up their claims. Additionally, it has not yet been approved for human use anywhere in the world [2, 3].
Ostarine is being researched for its ability to improve serious muscle wasting diseases. Interestingly enough, it is one of the few SARMs still in clinical trials while most others proved to be toxic. It may be approved for clinical use if the trials attest to its favorable benefits/risks ratio .
However, its use in professional sports will almost certainly remain illegal. The World Anti-Doping Agency banned Ostarine under the S1 Anabolic Agent category of the Prohibited List, along with all other SARMs back in 2008.
Ostarine is a selective androgen receptor modulator (SARM) touted to boost muscle mass. Although banned in professional sports, it’s still being medically researched.
- Increases lean muscle mass and strength
- Shouldn’t cause hormonal imbalance
- May improve bone strength
- May lower cholesterol and improve insulin resistance
- No clinical data to back up proponents’ claims
- Not allowed for use in professional sports
- Not approved for human use
- Effects and efficacy are unknown
- Short- and long-term side effects have yet to be investigated
- Long-term risks and safety are unknown
- Drug interactions remain unexplored
- Products sold online are not intended for human use
- These products usually contain a mix of dangerous, unapproved drugs
Mechanism of Action
It’s no secret that androgens increase skeletal muscle mass – that’s the main reason why men typically have more muscles than women. The activity of androgens in the body goes well beyond muscle-building, though. When sensors for androgens are non-selectively stimulated by drugs like steroids, it usually results in a long list of side effects.
SARMs are hypothesized to target muscles and increase anabolic processes while sparing the reproductive organs. Among many synthesized SARMs, the structure of Ostarine seems to offer some potential “advantages.”
In one study on mice, Ostarine was as effective as the most influential androgen, dihydrotestosterone, at restoring the size of pelvic floor muscles. Muscles in the pelvic floor are especially rich in androgen receptors (AR) .
Ostarine could also activate muscle stem cells (satellite cells), which help remodel and regenerate muscles. Surprisingly, it turned out that Ostarine also stimulates cells in the connective tissue, which are important for a successful recovery from muscle injuries .
However, we can’t make any conclusions based on data from cellular studies. Many drugs show some “promise” at the cellular level, only to be abandoned due to a lack of efficacy or risk of toxicity in later animal or human studies.
Although Ostarine is believed to target androgen receptors in muscles while sparing reproductive organs, no data backs this hypothesis up. Clinical studies are lacking.