Ostarine (MK-2866 / Enobosarm)

1. What It Does

Ostarine, also known as MK-2866 or Enobosarm, is a Selective Androgen Receptor Modulator (SARM) developed by GTx, Inc. It was originally created to treat muscle wasting associated with diseases such as cancer, osteoporosis, and age-related sarcopenia.

Ostarine selectively binds to androgen receptors in muscle and bone tissue, promoting anabolic activity without significantly affecting the prostate or other androgen-sensitive organs. Unlike anabolic steroids, Ostarine aims to provide the benefits of androgens (like testosterone) while minimizing unwanted side effects.

Mechanism of action:

• Stimulates muscle protein synthesis.

• Promotes nitrogen retention and lean mass gain.

• Triggers anabolic effects without converting to estrogen or DHT.

2. Main Reported Benefits

• Increased Lean Muscle Mass: Clinically shown to help preserve or build muscle, especially in calorie-restricted or catabolic states.

• Improved Strength: Users often report noticeable strength gains within weeks.

• Fat Loss Support: Often used in cutting cycles to maintain muscle while reducing body fat.

• Joint Healing & Bone Health: Anecdotal reports suggest improved joint comfort and bone mineral density.

• No Aromatization: Does not convert to estrogen, reducing the risk of gynecomastia or water retention.

• Minimal Liver Toxicity: Unlike oral steroids, Ostarine is not methylated, so liver strain is considered low.

3. Normal Applications

Ostarine has been studied for both therapeutic and performance-enhancing applications:

• Muscle Wasting Disorders: Clinically investigated for use in cancer cachexia and age-related sarcopenia.

• Osteoporosis and Fracture Healing: Explored for its benefits on bone health and strength.

• Athletic and Aesthetic Enhancement: Used by bodybuilders and athletes during bulking or cutting phases to improve physique and performance.

• Rehabilitation and Recovery: Used experimentally to aid in recovery from injury or surgery.

Though Ostarine has completed several human clinical trials, it remains unapproved by the FDA and other regulatory bodies for medical use.

4. Common Side Effects

While generally well-tolerated, Ostarine may still produce side effects, particularly at higher doses or with extended use:

• Testosterone Suppression: Mild to moderate suppression of natural testosterone production, especially at doses above 20 mg.

• Lethargy or Fatigue: Sometimes reported during or after cycles.

• Headaches or Back Pain: Occasionally noted in anecdotal reports.

• Mild Estrogenic Effects: Though Ostarine does not aromatize, elevated testosterone can indirectly raise estrogen, potentially causing water retention or slight mood changes.

• Increased SHBG: May affect hormone balance in extended use cycles.

Ostarine does not appear to be hepatotoxic, making it safer than oral anabolic steroids for the liver.

5. Recommended Administration or Dosage

Note: The following dosage information is based on clinical studies and anecdotal reports. Ostarine is not legally approved for over-the-counter use.

• Dosage Range: 10–25 mg per day

• Administration: Oral, once daily (long half-life supports single dosing)

• Cycle Length: 6–8 weeks common; longer cycles should include monitoring

• Half-Life: ~24 hours

• Post-Cycle Therapy (PCT): Typically recommended after cycles longer than 4–6 weeks or above 15 mg/day, especially to restore testosterone levels.

Lower doses (~10 mg/day) are often used for cutting or lean recomposition, while higher doses (~20–25 mg/day) are used for bulking or strength cycles.

Final Notes and Disclaimer

Ostarine is one of the most researched and well-tolerated SARMs, with human clinical data supporting its effects on muscle and bone health. However, it remains a research chemical, and its long-term safety profile in healthy individuals is still unknown. Misuse can result in hormonal imbalances or other health risks.