Ostarine [MK-2866], Enobosarm: Benefits, Uses, Side Effects

One of the latest trends in bodybuilding – selective androgen receptor modulators otherwise known as SARMS. One of the most extensively studied and popular SARMS is MK-2866, otherwise known as Ostarine or Enobosarm.

What Is MK-2866 (Ostarine) Enobosarm 

Ostarine, also known as MK-2866, MK-0773, GTx-024, and Enobosarm, is an oral nonsteroidal selective androgen receptor modulator (SARM). Formerly under the development of the pharmaceutical company Gtx and Merck, for the treatment of muscle wasting and osteoporosis, MK-2866 has become increasingly popular with athletes due to the associated anabolic effects and ergogenic benefits.

How Does MK-2866 Ostarine Work 

Ostarine was first investigated in the 1990s, developed by GTx and further investigated under Merck. As of 2012, the mechanism of action of Enobosarm are still being debated and requires further investigation.

SARMS are not anabolic steroids; rather, they are synthetic ligands that bind to androgen receptors. Depending on their molecular structure, they act as agonists, partial agonists, and antagonists. It is thus in a selective manner, that SARMS modulate or mediate coregulators and transcription factors or signaling cascade proteins to promote anabolic activity.

Studies have shown that ostarine, has a significant effect on the intensity of lipid metabolism. Ostarine downregulates the expression of leptin and adiponectin mRNAs. Leptin is one of the hunger hormones, that provides the sensation of satiety, or being full. According to preliminary trials, ostarine acts via androgen receptors with a similar effect as testosterone in the regulation of lipid metabolism [R].

Selective androgen receptor modulators such as ostarine demonstrate safer therapeutic profiles as compared to androgens like testosterone. Animal studies have shown that MK-2866 can improve bone density and lean muscle mass, while having limited effects on other androgen responsive tissues such as the prostate [R]. These same results were replicated in phase I human clinical trials [R].

Benefits Of MK-2866 (Ostarine)

Improves Lean Muscle Mass

In August of 2011, MK-2866 entered into Phase II clinical trials, investigating the effects on Cachexia, also known as muscle wasting. Cachexia, is a complex metabolic condition characterized by loss of skeletal muscle and a decline in physical function.

A 12-week double-blind, placebo-controlled phase II clinical trial was conducted to evaluate GTx-024 in 120 healthy elderly men, with the primary endpoint to increase lean body mass and secondary endpoint an improvement in physical function.

After 12 weeks at a 3mg application, significant improvements were seen in total body mass and physical function [R].

Two additional studies, one investigating the effects of enobosarm on muscle wasting in patients with cancer, found positive improvements in lean muscle mass, without toxic effects associated with anabolic or androgenic agents [R].

Similar results were observed in a randomized, prospective, double-blinded study of 170 sarcopenic women without cancer [R].

Side Effects Of MK-2866 (Ostarine)

Side effects of ostarine are dose dependent. Most common noted side effects are headache and backpain. Changes in libido specifically sex hormone-binding globulin (SHBG) can also change and decrease [R]. 

Unlike anabolic agents, SARMs do not undergo aromatization or 5-alpha reduction, and this may also contribute to their prostate-sparing effect.

Aromatization is the biochemical process in which aromatase catalyzes the conversion of testosterone into estradiol or Estrogen. Aromatization converts a nonaromatic ring into an aromatic ring and is catalyzed by aromatase, a P450 enzyme. Aromatization converts androgens into estrogens. Estrogens contain an aromatic six-carbon ring. Androgens do not.

Since ostarine does not aromatize into Estrogen directly, however, via the suppression of natural Testosterone levels, it can create an unfavorable balance between Testosterone and Estrogen in the body, elevating Estrogen levels. 

This can result in symptoms such as

  • Acne
  • Low Libido
  • Lethargy
  • Gynecomastia
  • Depressive Mood State
  • High Blood Pressure
  • Change in testicular size

Ostarine will suppress natural testosterone levels and endocrine function. Post-cycle therapy is advised, if taken to induce and restore normal healthy levels of testosterone.

Any anabolic agent, SARMS or not, increase androgen activity. While ostarine is selective for muscle and bone relative to androgen modulation there is still potential for androgen related side effects.

Anabolic agents are well known to cause liver damage which may manifest with elevated liver enzymes. Selective androgen receptor modulators (SARMs) have been heavily marketed as alternatives to androgenic anabolic steroids (AASs) for muscle gain and physical performance because of their perceived superior side-effect profile. 

At therapeutic dosages, there appears to be a low risk associated with use and liver damage. However, it should be noted, that any anabolic modulator may have some degree of liver toxicity with ergogenic dosages.

Is Ostarine Legal 

Ostarine, also known as MK-2866, MK-0773, GTx-024, and Enobosarm is classified as experimental.

Ostarine is classified as an investigational new drug by the FDA, meaning that it is still being studied and has not been approved for human use. As such, it is illegal to sell or distribute ostarine in the U.S. for any purpose other than FDA-approved clinical trials. 

Thus, it is legal to sell and buy SARMs that are marketed for research purposes, which commonly occurs online. However, it is illegal to sell and buy those that are packaged in capsules for human consumption and/or labeled as dietary supplements. Furthermore, SARMS cannot be marketed to the public as dietary supplements, and claims regarding their benefits cannot be made.

SARMs were banned by the World Anti-Doping Agency in January 2008, despite no drugs from this class yet being in clinical use, and blood tests for all known SARMs have been developed.

Ostarine, MK-2866: Takeaway

Although there have been promising clinical results in regards to improvements in lean body mass, and improve androgenic activity associated with ostarine application, further investigational studies are needed to determine the long-term risks and toxicity associated with its use as a performance enhancing agent. Currently, evaluated research indicates, that the etiology of ostarine, can cause suppression of natural testosterone levels due to the extreme selectivity of the androgen receptor. 

Swolverine is no way supports or condones the use of illegal or nefarious substances or compounds. This article is for informational and research purposes only.

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