Steroidal androgen-receptor research compound · Fact sheet
YK-11
Also known as YK11
YK-11 is a steroidal androgen-receptor research compound often marketed as a SARM or myostatin inhibitor. Follistatin expression in cultured mouse muscle cells does not establish safe human myostatin inhibition or muscle enhancement.
What is YK-11?
YK-11 has a steroidal chemical structure, unlike many nonsteroidal SARMs.
The myostatin claim is usually inferred from cell-level follistatin findings rather than direct human clinical outcomes.
Benefits & claims
Interest includes performance or metabolic effects, but a mechanism, hormone change or lean-mass result does not establish safe improvement in athletic function.
What the evidence supports
- YK-11 acted as a partial androgen-receptor agonist in laboratory assays.
- Mouse muscle-cell differentiation involved increased follistatin expression.
- These findings cannot establish human hypertrophy, strength, fertility safety or a treatment regimen.
Research areas
- Performance-related biology
- Clinical or preclinical disease research
Dosage & frequency
No established human regimenThe reviewed sources do not establish a human treatment amount or frequency for YK-11. Animal and laboratory exposures are not human regimens.
How to read these amounts
An approved regimen belongs to a specific product, indication, and population. A study regimen describes what researchers tested; it does not establish a prescription or a safe self-use protocol. Products, routes, and formulations are not interchangeable. A prescriber uses the full label and individual clinical circumstances.
Personal accounts may describe amounts, schedules and outcomes beyond clinical research. They do not establish a regimen. Read the reported experiences
Formulations, interactions & practical context
- Identity and pharmacology
- YK-11 has a steroidal chemical structure, unlike many nonsteroidal SARMs.
Formulation differences
- The myostatin claim is usually inferred from cell-level follistatin findings rather than direct human clinical outcomes.
Interactions & precautions
- The reviewed sources do not establish a comprehensive human interaction profile for this exact substance or combination.
What is still unresolved
- Long-term clinically meaningful benefit
- Endocrine, cardiovascular and organ safety
- Identity, exposure and interaction differences outside research settings
Side effects & risks
- Human endocrine, reproductive, liver and cardiovascular effects are insufficiently characterized.
- The SARM label does not remove steroid-related or other systemic risks, and product characterization may be uncertain.
This is a summary of the cited evidence, not a complete product label. A lack of human safety data does not establish safety.
Clinical research
Limited or unclear evidenceThe cited primary work uses receptor assays, cultured muscle cells and osteoblast-line experiments. Human therapeutic benefit is not established.
Studies
Androgen-receptor assay and partial-agonist characterization.
C2C12 muscle-cell follistatin and differentiation study.
Osteoblast-line proliferation and differentiation experiment.
Personal experiences
Reports describe what someone noticed. They cannot establish cause, typical results, or how often a side effect happens. Amounts and schedules describe the individual account, not an effective or safe dose. Product identity and strength may be unverified, and missing details are left explicit.
No attributable personal accounts were found in the sources reviewed.
Approval status
YK-11 has no FDA-approved therapeutic product. The cited research does not establish an approved performance-enhancement use.
Preclinical evidence; no FDA-approved product
Approval covers the labeled product, use and population. A trial phase does not establish success; a stopped program is not ongoing research.
- (17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester (YK11) is a partial agonist of the androgen receptor.
- Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression.
- Selective Androgen Receptor Modulator, YK11, Up-Regulates Osteoblastic Proliferation and Differentiation in MC3T3-E1 Cells.
- FDA: serious risks of SARM bodybuilding products
Open questions
- Long-term clinically meaningful benefit
- Endocrine, cardiovascular and organ safety
- Identity, exposure and interaction differences outside research settings
Summary
These findings cannot establish human hypertrophy, strength, fertility safety or a treatment regimen.
Sources
Medical evidence and regulatory sources are listed here. Personal reports are linked separately in the experiences section.
- pubmed(17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester (YK11) is a partial agonist of the androgen receptor.
Androgen-receptor assay and partial-agonist characterization.
- pubmedSelective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression.
C2C12 muscle-cell follistatin and differentiation study.
- pubmedSelective Androgen Receptor Modulator, YK11, Up-Regulates Osteoblastic Proliferation and Differentiation in MC3T3-E1 Cells.
Osteoblast-line proliferation and differentiation experiment.
- fdaFDA: serious risks of SARM bodybuilding products
FDA class-level warning: unapproved products, liver injury and cardiovascular and hormone-associated risks; not a compound-specific incidence estimate.