YK-11
YK11
YK-11 is a synthetic steroidal compound with hybrid activity that is commonly grouped with the SARM class but is mechanistically distinct. Structurally derived from 5-alpha-dihydrotestosterone (DHT), it was first described by Yasuhide Kanno (the name reflects his initials) in 2011. In addition to partial agonist activity at the androgen receptor, YK-11 uniquely downregulates myostatin signaling by modulating follistatin (FST) expression, which places it in a separate pharmacological category than classic SARMs like ostarine or ligandrol.
Take once or twice daily given the ~6-12 hour estimated half-life - splitting doses may provide more stable coverage. Plan comprehensive pre, mid, and post-cycle bloodwork (total and free testosterone, LH, FSH, estradiol, lipid panel, ALT/AST, CBC). Plan a full PCT (Nolvadex 20mg/day or Clomid 25mg/day for 4 weeks) for every cycle. Cycles should be SHORT (4-8 weeks maximum).
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
YK-11 has dual activity. First, it binds the androgen receptor (AR) as a partial agonist with tissue-selective properties similar to SARMs, driving muscle protein synthesis and nitrogen retention in skeletal muscle. Second, and more distinctively, it modulates the myostatin-follistatin axis: it increases expression of follistatin (FST), an endogenous myostatin inhibitor, which lifts the ceiling on muscle growth by reducing the negative regulator of satellite cell activation.
Myostatin is a member of the TGF-beta family and normally acts as a brake on skeletal muscle growth. By increasing follistatin, YK-11 effectively releases that brake, producing anabolic effects beyond what AR binding alone would predict. This dual mechanism is the basis for user reports of muscle hyperplasia claims, though direct human evidence is limited.
As a steroidal DHT-derivative, YK-11 carries the hepatic concerns of C17-alpha-alkylated-style orals (though it is not a formally 17-aa compound, the steroid backbone plus oral delivery produces hepatic stress). It does not aromatize to estrogen but produces HPT-axis suppression similar to other strong SARMs. Hair loss in genetically predisposed users is possible given the DHT-derived structure.
What to expect
First 1-2 weeks: onset is moderate - some strength improvement but effects build slowly. GI tolerance usually develops within the first week.
Weeks 3-5: visible muscle accrual, continued strength climb, reports of improved fullness. Mid-cycle liver panel essential.
Weeks 6-8: peak benefits. Cycle end recommended by week 8 due to hepatic and HPT burden. PCT begins immediately after last dose.
Evidence
References for this compound are being re-checked against their source records. We are not showing them until each one is confirmed to support the claim it sits under.
Side effects & safety
Commonly reported
- Pronounced suppression of endogenous testosterone (PCT required)
- ALT/AST elevation (steroidal structure plus oral delivery is hepatically stressing)
- Lipid profile changes (HDL drop)
- Mild GI upset early in cycle
Less common & notes
- Hair loss acceleration in genetically predisposed users (DHT-derived backbone), mild acne or oily skin, mood changes, libido changes (usually dip during suppression), mild blood pressure elevation, headache, insomnia, testicular softening.
- In women: significant virilization risk plus hepatic concerns - not recommended.
- Rare but serious: cholestatic hepatitis, persistent HPT suppression, significant hepatic injury at supratherapeutic doses or prolonged cycles.
- Hepatic effects are generally more pronounced than with non-steroidal SARMs.
Pharmacokinetics
Estimated - limited human PK data
Estimated
Estimated
Oral bioavailability estimated moderate-to-high (limited published data)
Per dose - supports 1-2x daily dosing
Hepatic metabolism (steroidal substrate for CYP enzymes). Renal excretion of metabolites. Published PK data is limited.
Storage. Store at controlled room temperature (20-25°C / 68-77°F). Protect from moisture and light. Keep capsules in original container with desiccant when available. Liquid suspensions should be kept sealed and used within 12 months of opening. Shelf life typically 2-3 years from manufacture date for capsules, 1-2 years for liquid. Keep out of reach of children.
Regulatory status
YK-11 is NOT FDA-approved for any indication. Classified as a research chemical in the United States - not a controlled substance federally as of this writing, but banned by WADA, USADA, the NCAA, and most professional sports leagues. FDA has issued warnings against SARM and SARM-like sales in over-the-counter dietary supplements. Some US states have introduced legislation restricting SARM sales. Use falls outside regulated medical practice.
Put it to work
Calculate, log & track
Open YK-11 straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.
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The guide & community
The complete YK-11 walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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