YK-11

YK-11 is a steroidal androgen-receptor research chemical, not a peptide. It is commonly marketed as an oral capsule for muscle and strength, but its human record covers metabolite detection and one doping-control sample, not efficacy or safety.

tier F · androgens · 0 controlled human efficacy trials

verdict

People seek YK-11 for muscle and strength. Mouse-cell studies measured partial androgen-receptor activity and increased follistatin expression, but they did not show direct myostatin blockade or human muscle gain. Human records are limited to urinary metabolites after administration and one doping-control sample.

the core tension

YK-11 has a defined steroidal structure, reproducible androgen-receptor activity in cells, and documented human detection. It still has no controlled human muscle, strength, body-composition, safety, or parent pharmacokinetic study.

what it is

YK-11 is a synthetic steroidal small molecule and partial androgen-receptor agonist, not a peptide. Its published structure is C25H34O6 at 430.5 Da, with a 19-norpregnane core and a C17/C20 spiroketal. It is grouped with SARMs because of its receptor profile, but the molecule remains steroidal.

what it does

In C2C12 mouse myoblasts, YK-11 produced weaker androgen-receptor signaling than dihydrotestosterone and increased follistatin expression. Separate mouse osteoblast and rat bone-defect work reported osteogenic signals. None of those studies measured human muscle, strength, body composition, or direct systemic myostatin blockade.

origin

The first indexed androgen-receptor pharmacology paper appeared in 2011, followed by a 2013 C2C12 myoblast paper. Later work added cell, mouse, rat, horse, human metabolite, and doping-detection records. It never developed into a controlled human efficacy or safety program.

does it work

No controlled human study has shown muscle gain, strength gain, fat loss, body-composition change, or a safe exposure. A human elimination experiment identified 14 urinary metabolites, and a later case report detected YK-11 in a doping-control sample. Those records prove human contact and detection, not efficacy, safety, or a parent half-life.

key facts

• molecular formula: C25H34O6
• molecular weight: 430.5 g/mol
• amino acids: n/a (steroidal small molecule, not a peptide)
• half-life: unknown; no measured parent terminal half-life in humans or animals
• type: steroidal androgen-receptor partial agonist and functional SARM
• CAS: 1370003-76-1
• 0 controlled human efficacy trials
• 2 human metabolism or detection records
• 4 route-resolved animal rows shown
• 2011 first indexed receptor paper

frequently asked questions

What is YK-11?

YK-11 is a steroidal androgen-receptor research chemical, not a peptide. It is often marketed beside SARMs, but it has a steroidal 19-norpregnane structure.

Does YK-11 build muscle or increase strength?

No controlled human efficacy study has measured either outcome. Mouse myoblasts showed partial androgen-receptor activity and higher follistatin expression, which is a cell signal rather than proof of human muscle or strength gains.

Does YK-11 block myostatin?

Direct myostatin binding or systemic blockade was not shown. One mouse-cell study measured higher follistatin expression. That result does not establish myostatin inhibition in people.

How is YK-11 usually sold?

FDA documented YK-11 marketed in oral capsules. That market form is an unapproved product, not a validated human route or formulation.

Has YK-11 been used in people?

Yes, but the human record is narrow. A 2018 elimination experiment tracked urinary metabolites after administration, and a 2024 case report detected YK-11 in a doping-control sample. Neither measured efficacy or established safety.

What is the half-life of YK-11?

Unknown. Human and horse studies detected metabolites or parent material, but none reported a parent concentration-time curve with a terminal elimination half-life. Detection windows cannot supply that number.

Is YK-11 safe or approved?

No safe human exposure is established, and FDA identifies marketed YK-11 products as unapproved new drugs. YK-11 is prohibited in tested sport under WADA S1.2. Its US controlled-substance treatment requires a fact-specific legal analysis rather than a simple name lookup.

related peptides

• testosterone: the clinically characterized androgen comparator
• Nandrolone: another 19-nor androgen with controlled human data
• Trenbolone: another androgen with major human evidence gaps

reptides grades the research record and cites the literature behind every call. research reference only; not medical advice.