YK-11

What YK11 is claimed to do

YK-11 is sold on one distinctive claim: that it inhibits myostatin, the protein limiting how much muscle the body will build. If true, that would make it categorically different from everything else in the SARMs range. This section holds 7 lines from £49 to £138, averaging near £103.

Where the claim comes from

It rests on cell-culture work showing that YK-11 increased follistatin in muscle cells. Follistatin antagonises myostatin, so raising it should in principle reduce myostatin’s braking effect.

That is a real published finding and it is also a long way from a demonstrated effect in a person. Cell culture shows a mechanism is possible; it does not show it happens at achievable doses in living muscle, and no human study has tested it.

The structural point that matters more

YK-11 is not a non-steroidal compound like ostarine or RAD-140. It is a steroidal molecule derived from DHT, and it carries a methyl group of the kind associated with hepatotoxicity in oral steroids.

That single structural fact tells you more about the risk profile than the myostatin discussion does. Anyone treating YK-11 as a gentler alternative to an oral steroid has it backwards — structurally, it belongs closer to that group than to the non-steroidal SARMs it is sold alongside.

Suppression and support

YK-11 binds the androgen receptor and is suppressive. It should be planned for with post cycle therapy in the same way as any androgen, and liver markers deserve monitoring given the structure.

Against RAD-140 it is far less studied, which is saying something, since RAD-140 is itself thinly evidenced in humans.

What we can and cannot tell you

We can tell you what is in the section, what it costs and what the published work actually showed. We cannot tell you an effective dose, because no study has established one, and any number presented as authoritative is somebody’s guess repeated often enough to sound official. Supplier checks are in how to check a brand is genuine.

Why it is rarely a first choice

YK-11 sits in an awkward position: more structurally concerning than the non-steroidal SARMs, less characterised than the oral steroids it structurally resembles, and priced above both. The people who choose it are generally chasing the myostatin claim specifically, which remains unverified in humans.

Frequently asked questions

Does YK-11 actually inhibit myostatin?
It raised follistatin in cell culture, which would work against myostatin. No human study has confirmed the effect.

Is it a normal SARM?
No. It is steroidal and DHT-derived, unlike ostarine or RAD-140, which are non-steroidal.

Is it hard on the liver?
The methylated steroidal structure is the type associated with hepatotoxicity. Monitor liver markers.

Does it need PCT?
Yes. It binds the androgen receptor and is suppressive.

What dose is effective?
Unestablished. No dose-ranging study in humans exists for this compound.