YK-11 as Myostatin Inhibitor?

I’ve been doing a lot of research on different compounds and supplements for bodybuilding lately and found my trusted gear supplier has a bunch of sarms & vials of follistatin.

From what I have read it seems MK-11 increases follistatin production which in turn decreases myostatin which apparently limits how much / how fast you can gain. I have read that effectively administering actual follistatin via injection in humans is sketchy science at best but i know that there are people doing it. I also know that SARMS are in a sketchy category of research also but i’m strongly considering trying something to boost follistatin for later cycles, or maybe even in-between cycles. I’m naturally the tall skinny ectomorph type and hoping to trick my body into giving me results / composition closer to a mesomorph.

Anybody have any experience with, or links to bodybuilding focused articles on either of these compounds?

I have been on their MK - 677 (GH secretagogue) for about 2 months and off cycle for about a month. so far i have sustained all of my weight and gained about another 5lbs without any noticeable fat gain or bloating.

Structurally YK-11 is a steroid. It looks like a steroid when you see the chemical composition. If it were even remotely possible that it worked as a myostatin inhibitor then it would have undergone at least one clinical trial. It hasn’t. Nobody touched it. There’s a reason for that. Everything we know about it is based on a theoretical paper written by the inventor. Now, does it work as a steroid? Yeah, seems to. Anecdotal evidence says it kind of works. But the plural of anecdote is not data. So we have no real science, only speculation.

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Is there any proven myostatin inhibitors on the market right now? I see a lot of “this works” but nothing really convincing.

I found a few sources that suggest YK-11 increases follistatin expression

“YK11 treatment of C2C12 cells, but not DHT, induced the expression of follistatin (Fst), and the YK11-mediated myogenic differentiation was reversed by anti-Fst antibody. These results suggest that the induction of Fst is important for the anabolic effect of YK11.”

“Selective induction of follistatin mRNA was found to be the unique mechanism for YK11 activity, because the induction was not shown by DHT.[25]”

There are proper studies showing follistatin suppresses myostatin so if YK11 actually increases follistatin it would in turn be suppressing your myostatin right?

There are lots of other reasons they might not have looked at it in clinical trials including political, financial, with the sides being the similar to other DHT derived steroids. Maybe they just don’t want people looking like those mice with 4x the normal amount of muscle mass lol.

Every paper i find still calls it a SARM though.

I have been looking. Everything so far has seemed really sketchy or ridiculously expensive.


Ya iv seen some things to show potential but no real data that says this compound at x dose will lower or suppress myostatin by x amount.

Honestly after watching those mice videos it makes me wonder how safe a drug would be that really can suppress it.

The only thing that is proven is that follistatin inhibits myostatin, both are produced naturally. you can buy vials of follistatin but from what i read you need some pretty advanced techniques that involve some kind of modified virus carrier for it to be really effective.

Give it another few years I’m sure something will surface that’s cheap and easy it’s the American way. Until then il stick to tren lol

Im going to talk to my doctor about YK11 and see if there is a blood test for myostatin & follistatin levels that he can send me for. If there is, i’m gonna try it in the name of science lol. I trust the source i have and can be fairly sure its legit based on the other stuff i got from them.

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Listen very carefully: It. Will. Not. Work.

Causing differentiation in mouse cells in a test tube means absolutely nothing as far as how human muscle cells will interact with this drug.

What is the proper dose? You don’t know because it’s never been studied, ever.

Is it hepatotoxic? Based on the nomenclature you’d assume that yes, to at least some degree.

Does it offer something that no other tested, proven drug on the market can give you? No evidence to suggest it does.

We live in a world with trenbolone being as abundant as the clouds in the sky. You can get practically anything you want if you know where to look. So what possible upside is there to use this stuff vs the rest of the field? That’s a serious question. What is your reasoning, based on actual science, that tells you it’s worth trying instead of using something with a track record, clinical trials, and decades of user experiences?


I wasn’t planning on using this instead of common gear. My plan was to see if the difference would be worth adding it to a stack, and potentially use it to make the most out of my gear, diet and training depending on what my bloods look like after. If it could hypothetically make a 10lb difference on a 12wk cycle it would be worth it to me.

The pathways affected are different than steroids and GH therefore used side by side there could be a synergistic effect for those with higher levels of myostatin or low levels of follistatin if YK11 makes a significant impact on your levels.

Right now one of the sketchiest parts about SARMs is finding a quality source and i have one.

I was skeptical about mk677 but it exceeded my expectations. Im still skeptical about YK11 but just from other people’s personal logs I have seen, it’s unlikely to cause any catastrophic results from a couple moderate cycles.

Suggested dose is 5mg-10mg /day for 4-6 weeks.

My logic is that myostatin regulates skeletal muscle growth. YK11 is supposed to increase follistatin production which binds to myostatin and prevents it from putting a damper on your gains. I know myostatin levels vary from person to person and strongly influence a persons natural body type and composition. If you are genetically gifted with low levels of Myostatin there is a good chance it wouldn’t do much. If you have naturally high levels it could have a significant impact on how much lean mass you can put on. My question is how much will it help, if at all, and is it worth it.

A trial run with bloods would be the only answer I’d take as an absolute on this because it’s the only way to know for sure.

I know you are just looking out for me and the other users here by saying flat out that the claims are false and it won’t work because of the unknowns. I appreciate it. But my gut is telling me to try itjust once and get tested before, during and after, then share my results to add to the limited pool of knowledge on this compound.

On the flip side If my doc can’t get me the tests i need im not going to waste my time with it because there would be no way to tell if it was worth it or put a quantitative measure on its effects on follistatin which is the only reason i am interested in the compound.

Below is the writeup from the site I get my shit from who have been super helpful and knowledgable with quality gear. I trust that they arent just blowing smoke up peoples asses when they could simply hype and sell things that have a longer track record to protect their reputation which is huge to UGLs.


YK-11 is a selective androgen receptor modulator (SARM). YK-11 directly binds to the androgen receptors. Beside it being a selective androgen receptor modulator, YK-11 also functions as a myostatin inhibitor.

One of the most frequently reported effects of YK-11 is that of increased pumps and muscle fullness, with many users claiming that this effect is even greater than when stacking with other sarms. YK-11’s ability to build muscle has been compared to testosterone, far exceeding other SARM’s.

YK-11 has few side effects. Low level of suppression is possible in long term high dose use.

  • Lean size gains without water retention
  • Increase in muscular size and strength
  • Muscle hardening
  • Increase in Follistatin levels
  • Inhibition of Myostatin levels
  • No anabolic steroid side effects
  • Possibly allow you to far surpass your body’s genetics in regards to accrual of muscle mass
  • Increased muscular fullness and better pumps

YK-11 is dosed at 5mg per day for beginners and 10mg per day for advanced users. Cycle’s should run 4-6 weeks. Half-life is estimated at 6-10 hours. YK-11 can be stacked with other compounds for a big boost in muscle gaining potential. YK-11 is suited for cutting or bulking cycles and will excel in both uses.

There is evidence to suggest steroids boost your myostatin levels over time which cuts back on your gains towards the end of a cycle or after blasting and cruising for a while. If the claims are true about the follistatin increase from YK11 logically there would be a synergystic utility for the compound.

I assume this is the write up from the source’s website? If so then they got out of the gate with an error already. Stenabolic (SR9009) is an entirely different compound. Tread carefully my friend.