S-23 SARM – The Dark Horse of the SARM World 🧬💪

S-23 is one of the most potent SARMs available today, originally developed for male hormonal contraception. While it never reached the pharmaceutical market, research into its anabolic properties has made it one of the most sought-after performance-enhancing research chemicals for muscle building and fat loss.

⚠️ Disclaimer: S-23 is not approved for human use. All information here is for educational purposes onlyregarding animal research and in-vitro data.

Why Was S-23 Designed? 🧪

S-23 was created by GTx Inc. to act as a selective androgen receptor modulator with very high binding affinity — even higher than LGD-4033 or RAD-140.
The original pharmaceutical goal was to suppress sperm production without affecting libido, while simultaneously maintaining muscle mass. This meant it needed to be strong, selective, and orally bioavailable.

How It Works in the Body 🔬

S-23 selectively binds to androgen receptors in muscle and bone tissue, triggering anabolic activity similar to testosterone — but without the high conversion to DHT or estrogen.

Key mechanisms:

• High androgen receptor affinity → Greater muscle protein synthesis

• Suppression of LH and FSH → Reduces natural testosterone production (hence the contraceptive research)

• Positive nitrogen balance → Enhances recovery and growth during caloric deficits

• Possible reduction in fat mass → Via increased basal metabolic rate and nutrient partitioning

Potential Research Benefits (Animal Data) 📊

Effect

Evidence Source

Increased lean muscle mass

Jones et al., 2009 – GTx internal study

Enhanced strength performance

Preclinical rat models

Fat mass reduction

Dose-dependent decreases in animal studies

Bone density preservation

Positive impact on bone mineral content

Example: In one preclinical study, S-23 outperformed other SARMs in both strength gains and lean tissue preservationwhile also significantly reducing fat mass in animal models.

Side Effects Observed in Studies ⚠️

Even in research settings, S-23’s potency means it has notable effects:

• Complete suppression of natural testosterone (reversible with PCT in animal models)

• Darker urine reported in some anecdotal logs (potential kidney stress — unconfirmed)

• Possible increased aggression at high doses

Because of the strong suppression, most experienced researchers recommend pairing S-23 research with a post-cycle therapy (PCT) protocol in applicable models.

Why It’s Popular in the Performance Community 🏆

• Cutting & Recomp Cycles → Its fat loss + muscle retention combo makes it ideal in a calorie deficit

• Hardening Effect → Anecdotally gives muscles a “dry” and dense look

• Low Water Retention → No estrogen conversion, meaning less bloating compared to anabolic steroids

Where to Source S-23 for Research 🔍

When buying SARMs, purity and transparency matter. Here are two verified research supply sources:

• 🧬 Fusion Peptides – Use code ANDREW for 20% off your entire order (10% sitewide + extra 10% with code).

• 🔬 Kimera Chems – Use code ANDREW for 10% off your order.

Both companies provide COAs (Certificates of Analysis) for their products so researchers can verify quality before use.

Bottom Line

S-23 is one of the strongest SARMs ever developed — designed for pharmaceutical-grade hormonal control but now primarily studied for its anabolic and fat-reducing effects in non-human models. Its potency means it comes with equally potent suppression, so caution is critical in all research settings.

If you’re a researcher looking for pure, lab-tested S-23, these two vendors currently offer some of the best deals:

✅ Fusion Peptides – Code ANDREW for 20% Off
✅ Kimera Chems – Code ANDREW for 10% Off