The current information on the internet about YK-11, is some what incorrect and by no means complete. YK-11 is not a SARM. It's a testosterone (Test)/ 5-α-dihydrotestosterone (DHT) derivative a synthetic anabolic
steroid
above it are the chemical structures of Tests and DHT
( above is the chemical structure of YK-11).
YK-11 possess the same steroid backbone (see diagrams below) as all other chemicals classified as steroid hormones have a look>> (List of designer drugs)
To date no chemical classified as a SARMs possess a steroid backbone >> (Selective androgen receptor modulator).
(Structure of Ostarine)
(Structure of LGD-4033)
The first peer reviewed paper on YK-11 by Kanno Y et al 2011 suggested that "YK-11 is a partial agonist of the Androgen receptor and might act as selective androgen receptor modulator " ((17α,20E)-17,20-[(1-methoxyethylidene)bis(oxy)]-3-oxo-19-norpregna-4,20-diene-21-carboxylic acid methyl ester (YK11) is a partial agonist of the an... - PubMed - NCBI ). A subsequent paper in 2013 by Kanno Y et al further investigating the molecular mechanics of YK-11 named it as a SARM in the papers title (Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression.). Research carried out by Kanno Y et al is scientifically sound but labelling this steroid as a SARM was incorrect.
It can be argued that because no nomenclature (Nomenclature) exists for classifying chemicals as SARMs, calling YK-11 a SARM is justified. However a quick look at steroid nomenclature confirms YK-11 is indeed a synthetic steroid have a look>> (3S-1)
If not labled a SARM by mistake my guess as to why it was ladled so would be would be two fold:
1) To get media attention (but this will only snuff YK-11 out as a steroid) and
2) To secure further funding (perhaps for animal testing) into the effects of YK-11 as research is not cheap.
I would put my money on the second reason as being the most likely reason.
As inferred above YK-11 has no animal testing data only in vitro data on C2C12 cells obtained from mice myoblats cell line capable of differentiation. Not all muscle cells can differentiate. C2C12 experiments tell us that YK-11 has the potential to cause muscle differentiation at certain concentrations. This can't directly be translated into a human equivalent dose because we have no data on it's metabolism but we can speculate based on research we have on other synthetic steroids. But we have no safety data on it.
The internet media likely from a surface reading of papers by Kanno Y et al have concluded that YK-11 is be more potent than classic steroids and has less side effects than them. This has not been stated or proven in any of the papers on Yk-11 published by Kanno Y et al, instead it is speculated the safety parameters of YK-11 may be comparable to SARMs but no comparison has actually been made.
What we see a combination of collective enthusiasm of the people and marketing hype piggybacking on the SARM name. Make no mistake YK-11 is not a SARM and has absolutely no safety data, which you can only really get from toxicity studies using animals/humans.
Given that we now know that YK-11 is a designer anabolic steroid it likely possess the typical side effects associated anabolic steroid which we can now assigned to YK-11 >> (Anabolic steroid). YK-11 has 4 methyl (CH3) groups and so will likely prove taxing to the liver; SARMs have reduced liver toxicity profile because they have substituted methyl groups with Halocarbons. In addition, data produced by Kanno Y et al 2013 demonstrate that YK-11 induces the production of follistatin, a glycoprotein that inhibits myostatin a protein which inhibits myogenesis (the development/formation of new muscle tissue/fibers during embryonic development and also extant in adult muscle tissue). Follistatin is also associated with prostate growth and so being targeted as such (Follistatin as potential therapeutic target in prostate cancer.)
Sparsely speculating on the potential therapeutic effects of YK-11 using existing data is by no means correct and no one should assume so without doing their own critical assessment of the information available.
YK-11 is derivative of the anabolic steroid DHT, and as partial agonist of the androgen receptor it would activate the androgen receptor to give a submaximal response when inadequate amounts of DHT or Test are present. In the presence of overstimulation of androgen receptors say when excess amounts of DHT or Test are present YK-11 will act as a competitive inhibitor of androgen receptors . This is because partial agonists typically display both agonistic and antagonistic properties.
Current pharmacodynamic data on YK-11 present by Kanno Y et al has me speculating that YK-11 will operate as an Antiandrogen with some anabolic potential in low levels of Test/DHT.
As a derivative of DHT, YK-11 will likely have little or no significant clinical effect on muscle mass gains, but may aid muscle mass retention with an effect on muscle hardness, muscle strength, libido and other typical masculine phenotypes because it shares a similar chemical make up and mechanism of action to DHT. Also because YK-11 was chemically designed from ethisterone a ********* progestin (as stated in methodology section of the 2011 paper by Kanno Y et al) and also bares some chemical resemblance to ********* progestin Norethynodrel which was the first female oral contraceptive as well as the class of ********* progestin which followed from Norethynodrel, YK-11 will likely possess the ability to bind and activate or inhibit progestogen receptors; which comes with it's own sets of effects. However only androgen receptors have been looked at so far so it is unknown what else may YK-11 bind to.
In healthy adult males the effects of YK-11 on muscle building quality are likely to be submaximal because it is a partial agonist on the androgen receptor and so a healthy male may experience reductions muscle strength and hardness while a female may experience improvements. However the ability of Yk-11 to increase follistatin levels compared to DHT and other steroids is what makes it novel. However no pre-clinical, clinical data exists to confirm its therapeutic significance if any.
No chemical compound to my knowledge exists that displays follistain stimulating effects like that of YK-11 so no comparison can be made. DHT is known to have effects on the CNS (central nervous system) and so YK-11 may also possess such effects if it can cross the blood brain barrier.
To conclude, YK-11 is a synthetic steroid with anabolic and likely undiscovered progestin potential. Because YK-11 is partial agonist to the androgen receptor it will be in direct competition with Test and DHT for binding and so its anabolic activity may be reliant on its ability to stimulate follistatin. Because of its partial agonist competition with Test and DHT it may reduce anabolic activity in otherwise healthy males. To date no safety data or animal testing exist.
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Originally Posted by jimmyinkedup
