Description
What Is YK-11?
YK-11 is a steroidal selective androgen receptor modulator (SARM) that uniquely functions as both an androgen receptor partial agonist and a myostatin inhibitor. First described by Japanese researcher Yuichiro Kanno in 2011, YK-11 is structurally derived from the 19-nor steroid backbone but shows a pharmacological profile distinct from traditional anabolic steroids due to its selective receptor tuning and follistatin-inducing properties.
What distinguishes YK-11 from all other characterized SARMs is its dual mechanism: beyond direct androgen receptor start in muscle tissue, YK-11 boosts the production of follistatin, a glycoprotein that binds and neutralizes myostatin, the main negative regulator of skeletal muscle growth. By suppressing myostatin signaling, YK-11 effectively removes the natural ceiling on muscle hypertrophy, a mechanism that has created large research interest in muscle biology, cachexia models, and genetic control of muscle mass. The compound shows oral uptake and a half-life of about six to ten hours.
Key Features and Specifications
| Specification |
Detail |
| Product Name |
YK-11 |
| Dosage |
5 mg per capsule |
| Quantity |
60 capsules per bottle |
| Form |
Oral capsule |
| CAS Number |
1370003-76-1 |
| Cell-level Formula |
C25H34O6 |
| Cell-level Weight |
430.54 g/mol |
| Purity |
≥99% (HPLC verified) |
| Testing |
Third-party HPLC and MS test |
| Storage |
Room heat, cool dry place, away from light |
| Classification |
Steroidal SARM / Myostatin inhibitor |
Mechanism of Action: How YK-11 Works
YK-11 operates through a dual mechanism that is unparalleled among SARM compounds. First, it binds to androgen receptors in muscle and bone tissue as a partial agonist, starting anabolic gene expression programs including upregulation of myogenic differentiation factors and protein synthesis pathways. Second, and critically, YK-11 induces the expression of follistatin in C2C12 myoblasts, directly measured through increases in follistatin mRNA and protein levels.
Follistatin binds myostatin (GDF-8) with high affinity, preventing myostatin from starting its receptor (ActRIIB) and the downstream Smad2/3 signaling cascade that normally limits muscle growth. By increasing follistatin production, YK-11 effectively lifts the myostatin-imposed brake on muscle hypertrophy, allowing for muscle growth beyond what androgen receptor start alone can achieve. This mechanism mirrors the phenotype seen in myostatin-knockout animals, which show dramatically increased muscle mass.
In vitro studies confirm that YK-11 increases follistatin expression in a dose-dependent manner and that this effect is androgen receptor-dependent, linking both mechanisms into a unified signaling pathway. The compound also boosts protein kinase B (Akt) phosphorylation, further enhancing anabolic signaling in skeletal muscle cells.
Reported Research Applications and Benefits
Myostatin blocking research represents the main and most novel use for YK-11. The compound’s power to increase follistatin production provides researchers with an orally bioavailable tool for studying the myostatin-follistatin axis, muscle growth control, and the treatment possible of myostatin pathway tuning in muscle wasting conditions, genetic myopathies, and age-related sarcopenia.
Skeletal muscle hypertrophy studies have documented that YK-11 promotes muscle cell differentiation and increases myotube diameter in cell culture, with effects that exceed those produced by equivalent levels of DHT. This supraphysiological anabolic possible, driven by the mix of AR start and myostatin suppression, has made YK-11 a key compound in muscle biology research.
Bone body function research has shown that YK-11 boosts osteoblast differentiation through androgen receptor-mediated start of bone morphogenetic protein (BMP) signaling pathways. Increases in osteocalcin, osteoprotegerin, and alkaline phosphatase have been documented, suggesting uses in osteoporosis and bone regrowth studies.
YK-11 Dosage Information for Research
| Protocol |
Dosage |
Duration |
Notes |
| Standard research dose |
5–10 mg/day |
6–8 weeks |
Most often studied range |
| Beginner protocol |
5 mg/day |
6 weeks |
Assess response conservatively |
| Advanced protocol |
10–15 mg/day |
8 weeks |
Higher suppression expected |
| Timing |
Split AM/PM |
— |
6–10 hour half-life |
Due to YK-11’s steroidal structure and moderate half-life, research protocols often employ split dosing. The compound’s potent dual mechanism warrants conservative dose escalation, and full blood panel tracking including testosterone, LH, FSH, and liver function markers is recommended throughout research protocols. Post-cycle therapy is often incorporated in protocols lasting six weeks or longer.
YK-11 vs LGD-4033: Key Differences
| Parameter |
YK-11 |
LGD-4033 (Ligandrol) |
| Structure |
Steroidal (19-nor derivative) |
Non-steroidal |
| Mechanism |
AR partial agonist + myostatin inhibitor |
AR full agonist |
| Follistatin induction |
Yes (dose-dependent) |
No |
| Myostatin suppression |
Yes (via follistatin) |
No |
| Half-life |
6–10 hours |
24–36 hours |
| Suppression possible |
Moderate to major |
Major |
| Anabolic ceiling |
Elevated (myostatin reduced) |
Standard AR-mediated |
Storage and Handling Instructions
Store YK-11 capsules at controlled room heat between 20°C and 25°C (68°F to 77°F) in the original sealed container. Protect from direct sunlight, too much heat, and humidity. Under recommended storage conditions, YK-11 capsules keep full potency for at least 24 months from the date of manufacture. Do not freeze.
Why Choose PrymaLab YK-11 Capsules
Every batch of PrymaLab YK-11 undergoes rigorous independent third-party testing using HPLC for purity finding and mass spectrometry for structural identity confirmation. Each order includes a batch-specific Certificate of Test documenting ≥99% purity, heavy metal screening, residual solvent test, and microbial testing. Pharmaceutical-grade encapsulation delivers precise 5 mg dosing per capsule, and free priority shipping is included on all domestic orders.
Frequently Asked Questions About YK-11
How does YK-11 inhibit myostatin?
YK-11 does not directly bind or block myostatin. Instead, it boosts the production of follistatin, a naturally occurring glycoprotein that binds myostatin with high affinity and prevents it from starting its receptor (ActRIIB). This indirect blocking mechanism is androgen receptor-dependent and increases in a dose-dependent manner in cell culture models.
Is YK-11 a steroid or a SARM?
YK-11 is classified as a steroidal SARM. While its chemical backbone is derived from the 19-nor steroid scaffold, it shows selective androgen receptor tuning rather than the broad systemic androgenic activity of traditional anabolic steroids. Its myostatin-blocking properties via follistatin induction are unique among both SARMs and steroids.
What is the half-life of YK-11?
The estimated plasma half-life of YK-11 is about six to ten hours based on available pharmacokinetic data. This relatively short half-life supports split dosing protocols, with most research designs giving doses twice daily to keep more stable circulating levels throughout the study period.
Does YK-11 require post-cycle therapy?
Yes. Due to its steroidal structure and moderate suppressive possible, YK-11 research protocols lasting six weeks or longer often incorporate post-cycle therapy using SERMs such as enclomiphene or clomiphene. Full hormone panels before, during, and after research protocols are strongly recommended.
Can YK-11 be stacked with other compounds in research?
Published research protocols have studied YK-11 in mix with non-steroidal SARMs and non-hormonal compounds like GW-501516. The unique myostatin-blocking mechanism of YK-11 complements standard AR-agonist SARMs by addressing a separate growth-limiting pathway. Stacking protocols need full tracking due to cumulative suppressive possible.
Quality Assurance and Testing
PrymaLab enforces rigorous quality standards for all YK-11 products. Each production batch is independently tested by accredited third-party laboratories using HPLC purity test, mass spectrometry identity confirmation, heavy metal screening, residual solvent testing, and microbial assessment. Batch-specific Certificates of Test are provided with every order for complete analytical transparency and research records.
Research Disclaimer
YK-11 is sold strictly for laboratory research and scientific study purposes only. This product is not intended for human consumption, veterinary use, or treatment use. YK-11 has not been approved by the FDA or any control agency for medical use. Purchasers must be qualified researchers affiliated with accredited institutions or licensed research organizations. By buying this product, you confirm that it will be used exclusively in accordance with all applicable local, state, and federal regulations governing research materials.
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