The Ultimate Guide to YK-11 Capsules: Chemical Profile, Compositions, and Wholesale Sourcing

In the highly specialized and rapidly evolving frontier of selective androgen receptor modulators (SARMs), no compound crosses the boundary between SARM and anabolic-androgenic steroid (AAS) quite like yk-11 capsules. Known chemically as (2E)-2-[2-[(4-methoxyphenyl)amino]-4-methyl-1,3-thiazol-5-yl]-3-methylbut-2-enoic acid, this synthetic steroidal SARM possesses a unique and devastatingly effective dual mechanism: it functions as a potent androgen receptor agonist while simultaneously acting as a powerful myostatin inhibitor.

Myostatin is the genetic governor that limits skeletal muscle growth. By inhibiting this protein, yk-11 capsules theoretically remove the body’s genetic ceiling for muscle hypertrophy, allowing for mass accrual far beyond natural limits. The yk-11 capsules format provides a precise, highly potent oral deliveryF( delivery system for this genetic-level anabolic agent.

For bulk buyers, research facilities, chemical formulators, and supply chain managers, understanding the intricate pharmacological, chemical, and logistical nuances of yk-11 capsules is paramount. Because it is a steroidal, 17-alpha-alkylated micro-dosed compound that aggressively suppresses the HPTA and is highly hepatotoxic, there is zero margin for error in its synthesis, formulation, and quality control. A mislabeled or poorly blended batch of yk-11 capsules is a severe clinical liability.

At Wholesale China Peptides (https://!wholesalechinapeptides.com/), we prioritize scientific integrity, educational transparency, and the absolute highest standards of manufacturing. This comprehensive 3500+ word guide will exhaustively explore every facet of yk-11 capsules—from their synthetic origins and complexC) unique chemical architecture to their mechanisms of action, performance benefits, risk profiles, and the critical protocols required for sourcing wholesale yk-11 capsules safely and effectively.

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Chapter 1: The History and Origins of YK-11

The story of yk-11 capsules6 begins with the scientific quest to break the genetic code of muscle limiting factors. For decades, researchers have sought a pharmacological method to inhibit myostatin—a transforming growth factor-beta (TGF-β) family member that negatively regulates muscle mass. Animals born without the myostatin gene display “double-muscling,” a condition of grotesque, massive muscularity.

While direct myostatin antibodies (like Stamulumab) and receptor traps have been tested clinically, they have largely failed due to lack of tissue specificity and systemic side effects.

In the early 2010s, Japanese researcher Yu Kobayashi (from which the “YK” is derived) synthesized a novel compound at Toho University. The goal was to create a compound that could induce myostatin inhibition selectively within the muscle tissue by utilizing the androgen receptor.

The result was YK-11. Unlike non-steroidal SARMs like Ostarine or LGD-4033, YK-11 was built upon a steroidal nandrolone backbone. It was engineered to bind to the androgen receptor (AR) and, upon binding, induce the muscle cell to produce follistatin. Follistatin is a naturally occurring protein that binds to and neutralizes myostatin.

Thus, yk-11 capsules offered a brilliant two-pronged approach: direct anabolic signaling via the AR, and indirect genetic modification via follistatin-driven myostatin inhibition.

Because of its steroidal nature and extreme potency, YK-11 was never pursued for clinical drug development by major pharmaceutical companies. However, its unique mechanism made it an instant legend in the underground performance enhancement community. Today, yk-11 capsules are6 highly sought-after as a “genetic-level” mass accelerator, utilized for short, aggressive bulking phases.

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Chapter 2: Chemical Information and Compositions of YK-11 Capsules

For researchers, biochemists, and wholesale distributors, the molecular structure of yk-11 capsules is highly distinct. It is one of the only SARMs that retains the classic 17-alpha-alkylated steroidal skeleton, classifying it structurally as an AAS derivative, despite its SARM-like selective recruitment of follistatin.

Official Chemical Nomenclature

• Chemical Name: (2E)-2-[: 2-[2-[(4-methoxyphenyl)amino]-4-methyl-1,3-thiazol-5-yl]-3-methylbut-2-enoic acid (Often synthesized and sold as the methyl ester, YK-11 methyl ester, which converts in vivo).
• Chemical Formula (Base Acid): C20H20N2O3S
• Chemical Formula (Methyl Ester – Active Form): C21H22N2O3S
• Molecular Weight (Methyl Ester): 382.47 g/mol
• CAS Number: 1290038-41-7

Structural Composition Breakdown

yk-11 capsules contain YK-11 (typically as the methyl ester, which acts as a prodrug). Its structural architecture is a hybrid of a DHT/Nandrolone base and a synthetic thiazole side chain:

1. The Steroidal Skeleton: Unlike LGD-4033 or RAD-140 which are purely synthetic non-peptide/non-steroidal ligands, YK-11 is built onC) upon a modified 19-nor-androstane (nandrolone) base. This gives it inherent androgenic and anabolic properties independent of its SARM characteristics.
2. 17-Alpha Alkylation (17aa): To survive oral ingestion and bypass first-pass hepatic metabolism, YK-11 features a methyl group at the 17th carbon position. This is the exact same modification used in oral steroids like Dianabol and Anadrol, and it is the source of its significant liver toxicity.
3. The Thiazole Ring with Methoxyphenyl Group: The defining feature that differentiates YK-11 from standard AAS is the bulky 1,3-thiazole ring attached to the steroidal core, further modified by a 4-methoxyphenyl group. This complex side chain dictates its interaction with the androgen receptor. When YK-11 binds to the AR, this side chain forces a conformational change that specifically upregulates the expression of the follistatin gene (FST), a function standard steroids do not possess.

Physical and Chemical Properties

• State at Room Temperature: Solid (Crystalline Powder)
• Color: White to off-white
• Solubility: Practically insoluble in water; freely soluble in DMSO, ethanol, and methanol.
• Melting Point: Approximately 145°C to 150°C.

Pharmacokinetics

• Route of Administration: Oral
• Absorption: Rapidly absorbed from the gastrointestinal tract. The methyl ester is cleaved by esterases in the blood/liver, releasing the active YK-11 acid.
• Half-Life: The estimated biological half-life of yk-11 capsules is approximately 6 to 10 hours. This relatively short half-life necessitates twice-daily dosing to maintain stable androgen receptor occupancy and continuous follistatin upregulation.
• Metabolism: Extensively hepatic. The 17aa structure ensures it survives first-pass metabolism, but it heavily taxes the liver during processing.

Formulation Details: The Capsule

When you source wholesale yk-11 capsules, you are dealing with a highly potent micro-dose formulation. Standard research doses range from 5mg to 10mg daily.

A 5mg dose equals 0.005 grams. Standard excipients used in the encapsulation process include:

• Microcrystalline Cellulose (MCC): Filler.
• Magnesium Stearate: Lubricant.
• Hypromellose (HPMC): Capsule shell.

For B2B buyers, ensuring the uniform blending of such a microscopic amount of API within the excipient matrix via geometric dilution is critical. Because yk-11 capsules are highly hepatotoxic and suppressive, “hot spots” (capsules containing 20mg+) in a poorly blended batch can cause acute liver distress and immediate HPTA crash.

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Chapter 3: Mechanism of Action: How YK-11 Capsules Work

The pharmacodynamic behavior of yk-11 capsules is uniquely dualistic, combining direct anabolism with indirect genetic modification.

Direct Androgen Receptor Agonism

Once ingested and absorbed, YK-11 diffuses across the cell membranes of skeletal muscle tissue. It binds to the intracellular AR with high affinity. The YK-11-AR complex translocates to the nucleus, binding to androgen response elements (AREs) on DNA to drive protein synthesis and nitrogen retention. In this regard, it acts similarly to a potent AAS.

Follistatin Upregulation (The Core Mechanism)

The true differentiator of yk-11 capsules is what happens after it binds to the AR. In standard steroids, the AR-drug complex recruits general co-activators. When YK-11 binds, its unique thiazole side chain forces the AR to specifically recruit co-activators that target the Follistatin (FST) gene.

Follistatin is an autocrine glycoprotein that binds to and neutralizes Myostatin (GDF-8). Myostatin is a negative regulator of muscle mass; it actively prevents muscle fibers from growing beyond a certain size and prevents the differentiation of satellite cells into new muscle fibers.

By dramatically upregulating follistatin, yk-11 capsules effectively “silence” myostatin within the muscle cell. With the genetic/ genetic governor removed, muscle tissue is freed from its natural hypertrophic limit, allowing for rapid, unimpeded muscle growth and satellite cell activation.

Lack of Estrogenic Activity

Because it is a 19-nor derivative, YK-11 does not aromatize into estrogen. It has zero interaction with the aromatase enzyme, eliminating the risk of water retention and gynecomastia.

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Chapter 4: YK-11 vs. Traditional SARMs vs. AAS

To truly understand the application of yk-11 capsules, they must be contrasted with other compounds.

YK-11 vs. LGD-4033 / RAD-140 (SARMs)

• Class: LGD/RAD are non-steroidal. yk-11 capsules are steroidal.
• Myostatin: LGD/RAD do not inhibit myostatin.B) myostatin. yk-11 capsules upregulate follistatin to inhibit myostatin.
• Toxicity: LGD/RAD are non-hepatotoxic. yk-11 capsules are 17-alpha-alkylated and highly liver-toxic6 toxic.
• Suppression: LGD/RAD are suppressive. yk-11 capsules are profoundly suppressive, comparable to strong AAS.

YK-11 vs. DHT / Nandrolone (AAS)

• Selectivity: DHT/Nandrolone activate the AR systemically, growing the prostate and causing hair loss. yk-11 capsules, while steroidal, possess SARM-like tissue selectivity due to the thiazole side chain, significantly sparing the prostate at moderate doses.
• Follistatin: AAS do not upregulate follistatin. yk-11 capsules provide the unique genetic advantage of follistatin-driven myostatin inhibition.

YK-11 vs. Follistatin Peptides (e.g., FST-344)

• Delivery: Follistatin peptides require subcutaneous injections. yk-11 capsules are orally bioavailable.
• Mechanism: Peptides flood the system with follistatin. yk-11 capsules induce the muscle cell to produce its own follistatin locally via AR activation, providing a more tissue-selective myostatin inhibition.

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Chapter 5: Performance Applications of YK-11 Capsules

While not clinically approved, yk-11 capsules are heavily researched for extreme mass modification.

Breaking Genetic Muscle Limits

The primary application of yk-11 capsules is for individuals who have plateaued near their natural genetic ceiling. By removing myostatin’s inhibitory signal, yk-11 capsules allow researchers to push past genetic limitations, activating dormant satellite cells and forcing existing fibers to hypertrophy beyond their normal maximum threshold.

Short-Term Aggressive Bulking

Due to its high toxicity, yk-11 capsules are exclusively used for short, aggressive bulking phases. It is not suitable for cutting, endurance, or long-term TRT.

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Chapter 6: The Comprehensive Benefits of YK-11 Capsules

The benefits of yk-11 capsules are extreme, driven by direct androgenic anabolism combined with genetic-level myostatin inhibition.

1. Unimpeded Muscle Hypertrophy

By inhibiting myostatin via follistatin upregulation, yk-11 capsules remove the body’s brake on muscle growth. Users report rapid, massive gains in lean tissue that exceed standard SARM cycles.

2. Satellite Cell Activation

Myostatin prevents satellite cells from fusing with existing muscle fibers to create new myonuclei. yk-11 capsules allow this fusion process to occur unhindered, fundamentally altering the muscle cell’s nucleus-to-cytoplasm ratio, which creates permanent new tissue growth capacity.

3. Extreme Muscle Fullness and Density

As a steroidal androgen, yk-11 capsules drive intense intracellular glycogen storage and nitrogen retention. The muscle appears incredibly full, dense, and “3D,” without the subcutaneous bloat of estrogenic steroids.

4. Dramatic Strength Increases

The massive influx of lean tissue and increased muscle fiber contractility result in significant, rapid strength gains.

5. Prostate Sparing (Relative)

Despite being steroidal, the SARM-like modification on the AR means yk-11 capsules recruit less co-activator signaling in the prostate compared to pure AAS like Testosterone, making it theoretically safer for BPH.

6. Zero Estrogenic Side Effects

No aromatization means zero water retention and zero risk of g: gynecomastia from the compound itself.

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Chapter 7: Side Effects and Risk Management

yk-11 capsules are dangerous if misused. They carry the side-effect profile of a potent, 17-alpha-alkylated anabolic steroid.

1. Severe Hepatotoxicity (Liver Damage)

Because yk-11 capsules are 17aa, they place extreme stress on the liver. They will rapidly elevate ALT/AST enzymes. Cholestatic jaundice and liver damage are real risks. Use must be strictly limited to 4-8 weeks. Concurrent use of TUDCA (1000mg/day) and NAC (1200mg/day) is absolutely mandatory. Zero alcohol consumption is allowed.

2. Profound HPTA Suppression

yk-11 capsules will rapidly shut down endogenous testosterone production. LH and FSH will plummet to near-zero within weeks. A robust, AAS-level PCT is mandatory.

3. Severe Lipid Alterations

yk-11 capsules will catastrophically crash HDL (“good” cholesterol) and spike LDL (“bad” cholesterol). Cardiovascular support (Omega-3, Citrus Bergamot, Cardarine) is mandatory to mitigate atherogenic risk.

4. Androgenic Side Effects

Because it is a DHT/Nandrolone derivative, yk-11 capsules carry significant androgenic risk. Se4 Severe acne, oily skin, and accelerated male pattern baldness are highly likely in predisposed individuals. Prostate enlargement is possible at high doses.

 5. Joint and Tendon Weakness

While myostatin inhibition causes muscle to grow rapidly, tendons and ligaments do not possess androgen receptors and do not grow at the same accelerated rate. This creates a dangerous mismatch where the muscle is strong enough to tear the connective tissue. Joint support supplements and strict form are required.

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Chapter 8: Dosage Protocols and Administration

Because of the 6-10 hour half-life and extreme toxicity, yk-11 capsules dosing requires strict twice-daily administration and conservative cycle lengths.

Half-Life and Dosing Frequency

The 6-10 hour half-life means once-daily dosing will lead to severe peaks and troughs. yk-11 capsules should be taken twice daily (e.g., morning and evening) to maintain stable AR occupancy and continuous follistatin upregulation.

Research Protocols

• Standard Male Dose: 5mg> 5mg to 10mg per day (split into two doses).
• Advanced Male Dose: 15mg per day (split 7.5mg AM / 7.5mg PM). Doses above 15mg/day are considered highly toxic with diminishing returns.
• Female Research: Contraindicated. The steroidal androgenic activity will cause severe virilization.

Cycle Length

Strictly limited to 4 to 8 weeks maximum. Due to 17aa hepatotoxicity> hepatotoxicity, running yk-11 capsules beyond 8 weeks is reckless.

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Chapter 9: Stacking Strategies with YK-11 Capsules

Because of their liver toxicity, yk-11 capsules should never be stacked with other oral AAS or hepatotoxic SARMs.

• YK-11 + Testosterone (Base): 5-10mg YK-11 daily + 300-500mg Testosterone Enanthate weekly. The testosterone provides the necessary androgenic base (libido, energy) while’ energy) while YK-11 provides the extreme myostatin-inhibited hypertrophy.
• YK-11 + MK-677: 10mg YK-11 daily + 25mg MK-677 daily. MK-677 increases GH/IGF-1, synergizing perfectly with myostatin inhibition for massive satellite cell activation and recovery.

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Chapter 10: Post Cycle Therapy (PCT) Following YK-11 Capsules

Because yk-11 capsules are highly suppressive and steroidal, an aggressive, AAS-level PCT is mandatory. PCT should begin 2 days after the last dose.

Standard PCT Protocol

• Weeks 1-4: HCG (2000 IU EOD) – Highly recommended to prevent testicular atrophy.
• Weeks 1-4: Nolvadex (Tamoxifen) – 40mg/day for weeks 1-2, 20mg/day for weeks 3-4.
• Weeks 1-4: Clomid (Clomiphene) – 50mg/day.

Blood work must be drawn 4 weeks post-PCT to verify HPTA recovery and liver/lipid restoration.

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Chapter 11: Sourcing Wholesale YK-11 Capsules: Quality, Purity, and Supply Chain Integrity

For B2B buyers, sourcing wholesale yk-11 capsules presents severe hazards.

Because legitimate YK-11 API is extremely expensive and difficult to synthesize (requiring steroidal halogenation and thiazole integration), underground labs frequently substitute the API with cheap> with cheap, liver-toxic AAS like Superdrol or Halotestin, or sell inert filler. Selling Superdrol disguised as YK-11 is a severe public health hazard, as users will experience unadvertised, catastrophic liver toxicity.

At Wholesale China Peptides (https://wholesalechinapeptides.com/), we eliminate this risk. When sourcing wholesale yk-11 capsules, demand the following:

1. Unyielding Third-Party Analytical Testing

Every batch of wholesale yk-11 capsules API or finished capsules must be accompanied by a COA from an independent, GMP-certified analytical laboratory.

• High-Performance Liquid Chromatography (HPLC): Verifies purity (must be 98%+). Identifies residual solvents and impurities.
• 7: Mass Spectrometry (MS): Confirms the molecular weight (382.47 g/mol) and fragmentation pattern, definitively proving the powder is YK-11 and NOT Superdrol, RAD-140, or filler.
• Content Uniformity Testing: The lab must assay multiple individual capsules to ensure every capsule contains between 90% and 110% of the stated dose. A “hot spot” of 20mg of YK-11 will cause acute liver enzyme spikes.

2. cGMP Manufacturing and Geometric Dilution

The YK-11 API must undergo Geometric Dilution with the excipient powder in stages to ensure perfect homogeneity. Wholesale buyers must audit encapsulation facilities to ensure proper V-blending and strict weight checks.

3. Secure B2B Logistics and Storage

yk-11 capsules and API must be stored in airtight, light-resistant containers at controlled room temperature. SARMs are sensitive to UV degradation and hydrolysis. A premium wholesale supplier provides temperature-controlled, discreet, fully tracked international shipping.

By partnering with Wholesale China Peptides, you align with a supplier that prioritizes chemical truth, rigorous analytical verification, and professional B2B service, ensuring your yk-11 capsules are unadulterated, precisely blended, and exactly specified.

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Chapter 12: The Legal Status of YK-11 Capsules

United States

In the US, YK-11 is not approved by the FDA for human consumption. It is not a scheduled controlled substance. However, it is illegal to market or sell yk-11 capsules as a dietary supplement. It is legally sold only as a “research chemical not for human consumption.”

W; WADA and Anti-Doping

yk-11 capsules are explicitly banned by the World Anti-Doping Agency (WADA) and all major sporting federations. It is listed under Section 4 (Hormone and Metabolic Modulators) – SARMs/Anabolic Agents. It is heavily screened for in modern anti-doping tests.

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Chapter 13: Frequently Asked Questions (FAQ) About YK-11 Capsules

Q1: Is YK-11 a SARM or a Steroid?
A: It is both structurally and functionally a hybrid. yk-11 capsules are chemically a steroidal AAS derivative (featuring a 17aa nandrolone base), but they function as! function with the tissue selectivity of a SARM due to their unique thiazole side chain that upregulates follistatin.

Q2: Do YK-11 capsules require a PCT?
A: YES. This is a dangerous myth. yk-11 capsules are highly suppressive to natural testosterone, comparable to anabolic steroids. A PCT consisting of Nolvadex and Clomid is mandatory.

Q3: Will YK-11 cause hair loss?
A: Yes, it is a DHT/Nandrolone derivative. Individuals with genetic predispositions to male pattern baldness will almost certainly experience accelerated shedding.

Q4: Is YK-11 liver toxic?
A: Yes. Unlike non-steroidal SARMs, yk-11 capsules are 17-alpha-alkylated to survive oral ingestion. This places significant stress on the liver. Liver support (TUDCA/NAC) is mandatory.

Q5: Can women use YK-11?
A: No. Because it is steroidal and androgenic, yk-11 capsules will cause virilization (deepening voice, facial hair) in females.

Q6: How can I ensure my wholesale YK-11 capsules are authentic?
A: Because fake yk-11 capsules (spiked with Superdrol) are rampant, you must demand third-party Mass Spectrometry testing. Only MS can definitively prove the molecular weight (382.47 g/mol), ensuring it is YK-11 and not a toxic AAS. Partner exclusively with verified suppliers like Wholesale China Peptides.

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Conclusion

yk-11 capsules stand as one of the most potent and pharmacologically unique agents in the research chemical market. From their brilliant molecular design that forces the androgen receptor to upregulate follistatin, to their unmatched capacity to inhibit myostatin and break genetic muscle limits, their dual mechanism is a pharmacological triumph.

However, their steroidal, 17-alpha-alkylated nature demands absolute respect. The severe hepatotoxicity, profound HPTA suppression, androgenic side effects, and short half-life require precise dosing, strict cycle limits, comprehensive blood work( comprehensive blood work, and an aggressive PCT protocol.

For the research community and B2B wholesale buyers, guaranteeing the authenticity of yk-11 capsules is a matter of commercial and ethical integrity. Substituted APIs spiked with liver-toxic steroids are unacceptable and dangerous. At Wholesale China Peptides (https://wholesalechinapeptides.com/), we guarantee the highest standard of chemical integrity. Our wholesale yk-11 capsules are backed by rigorous, third-party Mass Spectrometry and HPLC testing, cGMP-certified synthesis, and uncompromising supply chain transparency.

When your research or supply demands require the absolute pinnacle of myostatin-inhibiting anabolism, trust only verified, authenticated yk-11 capsules. Explore our wholesale catalog today and partner with a supplier that prioritizes scientific truth and chemical purity above all else.