S-23 — Potent Investigational SARM — SARMs
One of the most potent non-steroidal SARMs studied, with research into male hormonal contraception. Preclinical data only.
Overview
S-23 is a non-steroidal SARM developed by GTx Inc. that has demonstrated potent anabolic activity in preclinical models. It is considered one of the strongest SARMs based on its binding affinity for the androgen receptor and its pronounced effects on muscle mass and fat reduction in animal studies. Uniquely among SARMs, S-23 has been investigated as a potential male hormonal contraceptive. In rat studies, S-23 produced complete and reversible suppression of spermatogenesis at doses of 0.1-0.3 mg/day, with fertility recovering within 100 days of discontinuation. This contraceptive effect results from potent suppression of LH and FSH, reducing intratesticular testosterone below the threshold needed for spermatogenesis. S-23 produced significant lean mass gains and fat loss in castrated rats, with effects comparable to or exceeding testosterone propionate. However, S-23 has NO human clinical trial data. All pharmacological data derive from rodent and cell-based studies. The compound is available on the gray market and used by bodybuilders at estimated doses of 10-30 mg daily, but the safety profile in humans is completely unknown. Given its potent HPG axis suppression and lack of human data, S-23 carries substantial risk for unsupervised use.
Indications
- Investigational: Male hormonal contraception (preclinical only)
- Investigational: Muscle wasting (preclinical only)
- Unapproved: Lean mass gains and fat loss (bodybuilding use)
Mechanism of Action
S-23 binds the androgen receptor with very high affinity, acting as a full agonist with pronounced anabolic effects in skeletal muscle
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| S-23 | 10-30 mg | Once daily | Bodybuilding doses — NO human clinical data; entirely extrapolated |
Evidence Grade
GRADE C
Safety & Contraindications
- NO human safety data exist — all data from rodent studies
- Potent HPG axis suppression — expected to cause near-complete testosterone suppression
- Reversible infertility (demonstrated in rats, unknown in humans)
- Potential hepatotoxicity — unstudied in humans
- Prostate effects uncertain — may lose tissue selectivity at high doses
- Aggressive behavior reported anecdotally by bodybuilding users
- Gray market products unverified for purity and identity