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YK11YK11 is a SARM that has a unique structure because it is a progestin, further showing that progestin based SARM’s and anabolics will play a key role in the future of bodybuilding.   Progestins are unusual because they are technically not anabolic steroids yet they may have other properties that build muscle like reducing myostatin and other unexplored mechanisms.

SARM’s are similar to anabolic steroids in effects, but don’t tend to have the side effects like hair loss, prostate issues and other androgenic effects!

SARM’s still do have liver toxicity, especially at the doses that are suggested for bodybuilders, so don’t believe that SARM’s are the “holy grail” of supplements.  They can still have many of the side effects of classic anabolic steroids, especially at high doses.


This SARM is unique because it has roughly the same anabolic strength of testosterone and a limited set of androgenic effects.  This makes it unique because most SARM based products have 30-50% of the anabolic effects of testosterone.  This shows that a pregnane based skeleton is capable of activating the androgen receptor and also having other mass building functions like inhibiting myostatin.

This combined effect makes YK11 a great mass builder in comparison to other SARM’s on the black market.  It also legitimizes the current crop of Pregnane based prohormones that are being sold by LG Sciences and other manufacturers.

YK11 shows a better ability to activate mass building cofactors like Myf5, MyoD and myogenin than even DHT does.   Myf5, MyoD and myogenin are signal proteins that induce muscles to grow. It’s a little strange that the researchers used DHT as their mechanism of comparison mainly because DHT is quickly reduced to less active forms in the muscle cell still, DHT has the ability to build muscle at the right concentration.


There are currently three main Pregnane skeleton steroids on the market in addition to the grey market YK11.  LG Sciences was the first company to release these and you can also find them in some other supplements now on the market.  Typically these are combined together but here they are:

  • 17beta-[1-ketoethyl]-androsta-1,4-diene-3-one,17a-ol – (1,4-OHP) – this is a prohormone to boldenone and also is likely to have similar cofactor activation as YK11.  It also may increase appetite and ease joint pain.
  • 17beta-[1-ketoethyl]-androstane-3-one,17a-ol – (5aOHP) – this prohormone to DHT gives a hardening effect with limited side effects and also similar cofactor activation as YK11.
  • 6-keto-pregn-4-ene-3 20-dione – 6-Keto-Progesterone – this is a purely anabolic SARM that likely inhibits myostatin and may activate additional transcription mechanisms in the cell, there-by increasing protein synthesis.
  • (17-alpha,20E) 17,20-[(1-methoxyethylidene)bis(oxy)] 3-oxo-19-norpregna-4,20-diene 21-carboxylic acid methyl ester – this is the chemical name for YK11.

YK11 shows conclusive proof that 21 carbon (pregnane) steroids can activate the androgen receptor and give an anabolic effect similar to testosterone without some of the side effects.