RAD-140 is not a peptide. It is a selective androgen receptor modulator, commonly known as a SARM. These are two fundamentally different classes of compounds with different structures, different mechanisms, and different effects in the body. The confusion between them is common because both show up in the same fitness and bodybuilding conversations, often sold by the same vendors.
What RAD-140 Actually Is
RAD-140, also called Testolone, is a synthetic small molecule designed to mimic some of the effects of testosterone in a targeted way. It belongs to a class called SARMs, which bind directly to androgen receptors in muscle and bone tissue. Unlike traditional anabolic steroids, SARMs were designed to be selective, activating androgen receptors in specific tissues while theoretically sparing others like the prostate. RAD-140 was originally developed as a potential treatment for conditions like muscle wasting and hormone receptor-positive breast cancer. A Phase 1 clinical trial in postmenopausal women with breast cancer has been completed, though results have not been published.
The key point: RAD-140 is a fully synthetic chemical compound. It is not derived from amino acids, and it does not occur naturally in the body.
How Peptides Differ
Peptides are short chains of amino acids, the same building blocks that make up proteins. They act as signaling molecules, essentially messengers that tell your body to do something it already knows how to do. Common performance-related peptides include BPC-157 (associated with tissue repair) and growth hormone-releasing peptides that stimulate your pituitary gland to produce more growth hormone.
The structural difference is straightforward. Peptides are biological molecules made from amino acids strung together in a chain. SARMs like RAD-140 are synthetic chemicals with a completely different molecular architecture. A peptide signals the body to ramp up its own processes. RAD-140 binds directly to androgen receptors and activates them, functioning more like a key fitting into a lock.
Why People Confuse Them
Several things blur the line between SARMs and peptides in popular discussion. They’re sold on the same websites, discussed in the same bodybuilding forums, and marketed with overlapping promises about muscle growth and recovery. Both occupy a gray area where they’re technically sold “for research purposes only” while clearly being marketed for human use.
One compound in particular fuels the confusion: MK-677, also known as Ibutamoren. It is frequently called a peptide in bodybuilding circles because it stimulates growth hormone release, similar to what actual peptides do. But MK-677 is not a peptide either. It’s a non-peptide small molecule that happens to mimic a peptide’s function. It’s also not technically a SARM, even though it’s often grouped with them. This kind of loose categorization in the supplement world is a major reason people end up unsure what RAD-140 is.
How RAD-140 Works in the Body
RAD-140 binds to androgen receptors with high affinity and specificity. In laboratory studies, it has shown tissue-selective activity, meaning it activates androgen receptors in some cell types but not others. Research published in Clinical Cancer Research found that RAD-140 activated androgen receptors in breast cancer cells but not in prostate cancer cells, which is the kind of selectivity that made SARMs attractive to drug developers in the first place.
This is completely different from how peptides work. A growth hormone-releasing peptide, for example, doesn’t bind to androgen receptors at all. It signals the pituitary gland to release more growth hormone, which then circulates through the body. The downstream effects (increased muscle protein synthesis, fat metabolism) may overlap with what SARMs promise, but the biological pathways are distinct.
Regulatory and Safety Status
RAD-140 is not approved by the FDA for any use in humans. The FDA classifies products containing SARMs as unapproved new drugs. In a 2025 warning letter to a company selling RAD-140, the agency stated that SARMs are not generally recognized as safe and effective, and noted that “life-threatening reactions, including liver toxicity, have occurred in people taking products containing SARMs.” The FDA also flagged potential increased risk of heart attack and stroke.
Case reports support these concerns. A case documented in Australian Prescriber described a man who developed severe liver injury after using RAD-140 for bodybuilding. His bilirubin levels on hospital admission were more than 35 times the upper limit of normal, and a liver biopsy confirmed cholestatic hepatitis, a pattern of liver damage consistent with anabolic steroid-induced jaundice.
The World Anti-Doping Agency lists RAD-140 on its prohibited list under the category “Other Anabolic Agents,” alongside other SARMs like ostarine and ligandrol. It is not classified under any peptide category. If you’re a tested athlete, RAD-140 will result in a doping violation.
SARMs vs. Peptides at a Glance
- Structure: SARMs are synthetic small molecules. Peptides are short chains of amino acids.
- Mechanism: SARMs bind directly to androgen receptors. Peptides act as signaling molecules that trigger the body’s own processes.
- Administration: SARMs like RAD-140 are typically taken orally in capsule form. Many peptides require injection because they break down in the digestive system.
- Primary targets: SARMs target androgen receptors in muscle and bone. Peptides vary widely, targeting growth hormone release, tissue repair, or immune function depending on the specific peptide.
- RAD-140 specifically: It is a SARM, not a peptide, not approved for human use, and banned in competitive sports.
The bottom line is simple. RAD-140 and peptides are as different as a synthetic drug and a fragment of protein. They share shelf space in the performance enhancement world, but they share almost nothing in terms of chemistry or how they interact with your body.