RAD-140 (Testolone) vs S-23

Mechanism

RAD-140 is a potent nonsteroidal SARM with high oral bioavailability and selectivity for muscle and bone AR over prostate. It acts as a full agonist at the AR in muscle tissue, promoting nitrogen retention and protein synthesis via mTOR/p70S6K pathway activation. RAD-140 also demonstrates neuroprotective properties, acting against beta-amyloid-induced neurotoxicity through AR-mediated MAPK/ERK signaling. Preclinical data show greater anabolic potency than testosterone propionate at equivalent doses with significantly reduced prostate stimulation.

Standard Dosing

Research indicates 10-20 mg daily orally for 8-12 weeks. Phase 1 clinical trial (oncology) identified 100 mg as the maximum tolerated dose.

Timing

Once daily, consistent timing. Very long half-life (~60 hours) means stable plasma levels even with once-daily dosing. Morning preferred.

Cycle Duration

8-12 week cycles. PCT mandatory due to significant HPG axis suppression.

Side Effects

• Significant testosterone suppression
• Hepatotoxicity (multiple published case reports of drug-induced liver injury)
• HDL suppression and LDL elevation
• Aggression and mood changes
• Hair shedding (androgenic effect despite 'selective' designation)
• Insomnia
• Headache

Contraindications

• Pre-existing liver disease
• Androgen-sensitive cancers
• Cardiovascular disease (LDL elevation concern)
• Pregnancy and breastfeeding
• Individuals under 21
• Athletes subject to anti-doping testing

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Mechanism

S-23 is one of the most potent nonsteroidal SARMs developed, originally investigated by GTx, Inc. as a potential male hormonal contraceptive. It binds the androgen receptor with very high affinity, producing near-steroidal anabolic effects in muscle and bone while profoundly suppressing FSH and LH, leading to oligospermia and azoospermia in animal models. S-23 increases lean body mass and bone mineral density while reducing fat mass in a dose-dependent manner. The contraceptive effect was fully reversible in rat studies — spermatogenesis and fertility recovered completely after a 100-day washout period.

Standard Dosing

Research indicates 10-25 mg daily orally for 8-12 weeks. No human clinical trials — dosing extrapolated from rat pharmacology and anecdotal reports.

Timing

Split into 2 daily doses due to relatively short half-life (~12 hours). Morning and evening dosing.

Cycle Duration

8 week cycles maximum recommended. PCT is absolutely mandatory due to profound HPG suppression. Allow full recovery before considering subsequent cycles.

Side Effects

• Profound testosterone suppression (near-complete LH/FSH shutdown)
• Temporary infertility / azoospermia
• Aggression and mood changes (reported frequently)
• Hair loss (strong androgenic binding)
• Testicular atrophy
• Night sweats
• Prostate effects (despite selectivity claims, S-23 had some prostate stimulation in rats)
• HDL suppression

Contraindications

• Desire for fertility in the near term (profound spermatogenic suppression)
• Pre-existing liver disease
• Androgen-sensitive cancers
• Cardiovascular disease
• Pregnancy and breastfeeding
• Individuals under 21

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