LGD-4033 (Ligandrol) vs YK-11

Mechanism

LGD-4033 is a potent nonsteroidal selective androgen receptor modulator with high AR binding affinity (Ki of approximately 1 nM). It demonstrates strong anabolic activity in muscle and bone with significantly reduced androgenic activity in prostate tissue, achieving an anabolic-to-androgenic ratio of approximately 10:1. LGD-4033 activates the AR with full agonist efficacy in muscle, upregulating the PI3K/Akt/mTOR pathway for protein synthesis and satellite cell recruitment. It produces dose-dependent suppression of SHBG, total testosterone, LH, and FSH, indicating significant HPG axis suppression even at low doses.

Standard Dosing

Research indicates 5-10 mg daily orally for 8-12 weeks. Phase 1 data showed significant lean mass gains at 1 mg/day.

Timing

Once daily, consistent timing. Half-life approximately 24-36 hours. No food timing requirements.

Cycle Duration

8-12 week cycles maximum. PCT strongly recommended after all but the shortest/lowest-dose cycles.

Side Effects

• Significant testosterone suppression (dose-dependent; occurs even at 1 mg/day)
• Suppressed SHBG, LH, and FSH
• Elevated liver enzymes / hepatotoxicity (case reports of cholestatic liver injury)
• HDL cholesterol suppression
• Headache
• Fatigue (late-cycle, from suppression)
• Water retention

Contraindications

• Androgen-sensitive cancers
• Pre-existing liver disease or elevated liver enzymes
• Pregnancy and breastfeeding
• Individuals under 21
• Athletes subject to WADA/anti-doping testing

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Mechanism

YK-11 is a synthetic steroidal compound classified as a gene-selective partial agonist of the androgen receptor. Uniquely among SARMs, YK-11 does not induce the N/C terminal interaction of the AR required for full transcriptional activation, instead selectively activating a subset of AR-dependent genes. Its primary distinguishing mechanism is potent induction of follistatin expression, which directly antagonizes myostatin — a key negative regulator of skeletal muscle mass. This dual action (partial AR agonism + myostatin inhibition via follistatin) theoretically provides anabolic stimulus beyond what full AR agonists alone can achieve.

Standard Dosing

Research indicates 5-15 mg daily orally for 6-8 weeks. No human clinical trials exist — all dosing data is anecdotal.

Timing

Split into 2 daily doses (morning and evening) due to presumed short half-life (~6-10 hours based on structural analysis). Consistent timing essential.

Cycle Duration

6-8 week cycles maximum. PCT strongly recommended. Avoid extended use due to unknown long-term safety profile.

Side Effects

• Testosterone suppression (expected — steroidal compound)
• Hepatotoxicity (17-alpha-alkylated structure implies liver toxicity risk)
• Joint pain and tendon issues (anecdotal — possibly from DHT-like drying effects)
• Hair loss (steroidal androgenic effects)
• Aggression
• Unknown long-term effects (no human studies)

Contraindications

• Pre-existing liver disease
• Androgen-sensitive cancers
• Cardiovascular disease
• Pregnancy and breastfeeding
• Individuals under 21
• Anyone unwilling to accept research chemical risk with zero human clinical data

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