Introduction
In the world of Selective Androgen Receptor Modulators (SARMs), one compound continues to draw attention for its extreme anabolic potential and tissue-selective action: RAD-140, also known as Testolone.
Originally developed by Radius Health, RAD-140 was designed to provide the muscle-building benefits of anabolic steroids—without the unwanted side effects such as prostate growth, liver toxicity, or estrogen-related complications.
Thanks to its powerful anabolic signaling, oral bioavailability, and favorable preclinical safety profile, RAD-140 has become a focal point of research in areas such as:
- Muscle wasting disorders
- Age-related sarcopenia
- Hormone replacement therapy (HRT) alternatives
- Neuroprotection
This blog dives into what RAD-140 is, how it works, the science behind it, and how it compares to other SARMs and anabolic agents in modern research.
What Is RAD-140?
RAD-140 (Testolone) is a non-steroidal selective androgen receptor modulator. It binds to the androgen receptor (AR) in muscle and bone tissue to promote anabolism (growth)—without activating ARs in reproductive organs or triggering estrogen conversion.
Designed To:
- Increase lean muscle mass
- Enhance strength
- Avoid androgenic and estrogenic side effects
- Provide a safer alternative to testosterone replacement therapy
Unlike traditional steroids, RAD-140 is orally bioavailable, does not convert to DHT or estrogen, and is being explored for its neuroprotective effects as well.
Mechanism of Action
RAD-140 binds selectively to the androgen receptor, triggering anabolic gene transcription in muscle and bone, while sparing other tissues like the prostate and skin.
Key Functions of RAD-140:
- Increases muscle protein synthesis
- Enhances nitrogen retention
- Stimulates muscle fiber hypertrophy
- Supports bone mineral density
- Preserves testosterone in animal models
What makes it stand out is its high anabolic-to-androgenic ratio, meaning it delivers muscle-building effects without common side effects associated with synthetic hormones.
Preclinical Research and Clinical Data
1. Muscle Growth and Lean Mass
In animal studies, RAD-140 has been shown to:
- Increase lean body mass significantly
- Stimulate myogenic gene expression
- Promote muscle regeneration following atrophy or injury
- Prevent muscle loss during caloric restriction
These effects were seen without prostate enlargement, differentiating RAD-140 from testosterone in safety-focused models.
2. Bone Health
RAD-140 has demonstrated:
- Increased bone formation markers
- Improved bone mineral density (BMD)
- Enhanced osteoblast activity
This suggests potential for use in osteopenia and osteoporosis research, particularly in postmenopausal or androgen-deficient models.
3. Neuroprotective Properties
One of the lesser-known benefits of RAD-140 is its effect on the brain:
- Preclinical studies show protection against neurodegeneration
- May shield neurons from amyloid beta toxicity
- Supports hippocampal growth and cognitive resilience
These effects are due to AR signaling in the central nervous system, where RAD-140 mimics the neuroprotective aspects of testosterone—without androgenic risk.
4. Hormone Replacement Research
RAD-140 is being investigated as a potential alternative to testosterone replacement therapy (TRT):
- Produces anabolic effects in testosterone-deficient models
- Minimizes androgenic and estrogenic side effects
- May avoid prostate complications common with testosterone
This makes RAD-140 an ideal candidate for research into male hypogonadism, muscle wasting diseases, and age-related hormone decline.
RAD-140 vs. Other SARMs
| Compound | Anabolic Strength | Suppression Risk | Water Retention | Goal |
| RAD-140 | Very High | High | Low | Hypertrophy & strength |
| LGD-4033 | High | Moderate | Low | Lean mass + strength |
| MK-2866 | Mild–Moderate | Low–Moderate | None | Muscle preservation |
| YK-11 | Extreme (myostatin mod) | Very High | None | Advanced hypertrophy |
| S4 (Andarine) | Moderate | Low–Moderate | None | Strength, cutting |
RAD-140 is widely considered the strongest SARM for anabolic output, making it a go-to choice in hypertrophy research.
Side Effects in Research
Despite being non-steroidal, RAD-140 can produce side effects due to its potent androgenic activity, particularly at high doses or prolonged use.
Common (dose-dependent):
- Testosterone suppression
- Headaches
- Mild aggression or irritability
- Sleep disturbances
- Hair shedding (rare, androgen-sensitive subjects)
Less Common:
- Lipid profile changes (reduced HDL)
- Mild liver enzyme elevation (especially if stacked)
- Appetite suppression or increase (individual variability)
In most research models, side effects were reversible after discontinuation, and no estrogenic effects (like gynecomastia) were reported.
RAD-140 vs. Anabolic Steroids
| Factor | RAD-140 | Anabolic Steroids |
| Tissue Selectivity | High | Low (systemic activity) |
| Estrogen Conversion | None | Common (aromatization) |
| Suppression | High (reversible) | Severe (may require PCT) |
| Liver Toxicity | Mild (depends on stack) | Often high (especially oral steroids) |
| Water Retention | None | Common |
| Acne / Hair Loss | Rare | Common |
RAD-140 provides comparable anabolic effects to moderate steroid cycles, but with lower estrogenic and hepatic risk in research models.
Legal and Regulatory Status
As of 2025, RAD-140 is:
- Not FDA-approved for any human use
- Classified as a research chemical
- Banned by WADA and all major athletic federations
- Illegal to sell for human consumption or bodybuilding purposes
Labeling Requirements:
“For laboratory research only. Not for human or veterinary use.”
Common Research Applications
RAD-140 is currently explored in various research domains:
1. Muscle Wasting and Sarcopenia
- Cancer cachexia models
- Age-related muscle loss
- Hormone-deficient anabolic resistance
2. Androgen Replacement Alternatives
- Andropause and low-T modeling
- Potential HRT analog in preclinical settings
- Bone and muscle preservation without prostate stimulation
3. Performance Science
- Lean mass gain in exercise studies
- Muscle regeneration following injury
- Resistance training adaptation and satellite cell activation
4. Neurological Research
- Neuroprotection in Alzheimer’s models
- Cognitive recovery and memory modulation
- Testosterone-linked neural regeneration studies
Dosing in Research Settings
Note: The following is based on clinical and preclinical trial data, not medical advice.
In animal studies and early trials:
- Doses ranged from 1 mg to 30 mg daily (oral)
- Higher doses correlated with more rapid lean mass increases—but also more testosterone suppression
Anecdotally, RAD-140 begins showing noticeable effects within 7–14 days, with peak results after 4–6 weeks in typical models.
Stacking in Research Contexts
Due to its strong anabolic nature, RAD-140 is often used as a foundation compound in stacked protocols:
| Stack Partner | Purpose |
| MK-677 | Enhances GH/IGF-1 axis + sleep recovery |
| GW-501516 | Improves fat loss + endurance |
| LGD-4033 | Mass gain synergy |
| BPC-157 / TB-500 | Tissue healing + anabolic support |
Caution is advised in stacking due to the compounding suppression effects of multiple SARMs.
RAD-140 at a Glance
| Feature | Description |
| Class | SARM |
| Target | Androgen receptor (AR) |
| Main Benefits | Muscle growth, strength, neuroprotection |
| Estrogen Conversion | None |
| Suppression Risk | High (reversible) |
| Route of Administration | Oral |
| Half-Life | ~16–20 hours |
| Legal Status | Research use only, not FDA-approved |
| WADA Status | Banned |
Final Thoughts
RAD-140 (Testolone) is a powerful, targeted anabolic agent with one of the highest anabolic-to-androgenic ratios in the SARM category. Its ability to:
- Stimulate lean mass growth
- Enhance strength
- Support bone health
- Offer neuroprotective benefits
—makes it one of the most versatile SARMs in preclinical anabolic research.
However, its potency comes with hormonal consequences, and researchers must weigh suppression risk, lipid impacts, and stacking strategies accordingly.
For muscle physiology, aging, or hormone replacement modeling, RAD-140 provides a highly effective tool—as long as it’s used responsibly, within legally and ethically compliant frameworks.
Disclaimer: RAD-140 is a research chemical not approved for human use. This article is for educational purposes only and does not constitute medical advice. Always follow local laws, safety protocols, and regulatory standards when working with or selling research compounds.
References
- Coss, C.C., et al. (2014). “Selective androgen receptor modulator RAD140 is a potent stimulator of lean muscle mass and bone mineral density.” ACS Medicinal Chemistry Letters.
- Narayanan, R., et al. (2015). “RAD-140: Preclinical evaluation and potential therapeutic uses.” Endocrinology.
- Kearbey, J.D., et al. (2007). “Tissue-selective activity of SARMs.” Journal of Pharmacology and Experimental Therapeutics.
- Radius Health, Inc. (2020). “RAD-140 clinical development summary.” ClinicalTrials.gov.
- WADA Prohibited List (2025). World Anti-Doping Agency.