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YK-11 15mg/ml x 30ml INFORMATION


YK-11 is a SARM that acts as a gene-specific agonist of the androgen receptor (AR) in MDA-MB 453 cells.

YK 11 works on a variety of different anabolic pathways. YK-11 has shown greater anabolic activity in vitro in C2C12 myoblasts than DHT [1, 2].

YK11 promoted a cascade of muscle growth and key myogenic regulatory factors in skeletal muscle tissue such as myogenic

differentiation factor (MyoD), myogenic factor 5 (Myf5), to a significantly greater extent than DHT.

This can in part explain why YK11 exerts its selective modulation of the AR. Unlike testosterone and most other androgen receptor mediated

anabolic agents, YK-11 is orally bioavailable so it does not require injection for proper absorption. At this time YK-11 is for laboratory research

use only and the side effects are not fully known.


YK11 Mechanism of Action

What really sets YK-11 apart is that a key component of its anabolic activity is modulated via expression of follistatin. They discovered this by co-administering anti-follistatin antibodies with YK 11 to measure the difference in effects [2]. Follistatin has been shown to promote insulin-stimulated glucose and amino acid uptake into skeletal muscle cells, improving insulin sensitivity directly and increasing skeletal muscle mass [3]. Follistatin proteins also block inhibitory ligands from binding to Transforming Growth Factor-ß [4].

Perhaps the most alluring effect of follistatin is binding and neutralizing of catabolic proteins Activin A, Activin B, and Myostatin. Unfortunately follistatin proteins themselves undergo rapid proteolysis and have limited bioavailability and half-life even when injected directly into a wasting muscle. YK-11 however stimulates the body to produce more follistatin proteins systemically and locally which may circumvent this shortfall of direct follistatin administration and promote muscle growth [2, 4].

Animal studies have investigated the effects of YK 11 as a potential treatment for sepsis-induced muscle wasting. Researchers observed protective effects on muscle tissue and organ tissue, as well as suppression of gram-negative bacteria induced cytokine inflammation. Mortality rate in eight-week old septic mice treated with YK-11 also decreased significantly. They concluded that this was due to the suppression of myostatin as well as an increase in the expression of the follistatin gene [5].


YK-11 Side Effects

Little is revealed in clinical studies regarding YK-11 side effects however anecdotal reports online indicate the potential for joint pain, mild male-pattern hair loss, and aggression. Due to its action upon the androgen receptor (AR) it is plausible that YK11 use or abuse may result in side effects commonly reported with the use of other anabolics, for example elevated hemoglobin or hematocrit, high blood pressure, insomnia, nausea, or liver damage. YK 11 is only approved for laboratory research purposes at this time and is not a dietary supplement.


Abuse Warning

YK11 is an investigational compound still awaiting FDA approval and is not a dietary supplement. At Mass to Brass LLC are not medical doctors, and our expertise is sourcing and quality control. Where we do not encourage or condone consumer use of SARMs products, they are for research purposes only. Anecdotal reports online indicate YK 11 dosage of 10mg and 20mg per day used by many individuals. A YK11 dose of 50mg per day has even been reported by several bodybuilders in online forums. These dosages may not match those used in carefully designed medical research protocols and may pose a serious risk of adverse effects in users.

We consider the duplication of anecdotal protocols online to be a risky practice. SARMs should only be used under the supervision and direction of a medical doctor or designated research authority. We strongly discourage the use of SARMs for performance enhancement in sports and bodybuilding, and warn against “bro science” and peer consensus when making decisions about human health.



1. Kanno Y, Hikosaka R, Zhang SY, Inoue Y, Nakahama T, Kato K, Yamaguchi A, Tominaga N, Kohra S, Arizono K, Inouye Y (2011). “(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 androgen receptor”. Biological & Pharmaceutical Bulletin. 34 (3): 318–23. PMID 21372378
2. Kanno Y, Ota R, Someya K, Kusakabe T, Kato K, Inouye Y (2013). “Selective androgen receptor modulator, YK11, regulates myogenic differentiation of C2C12 myoblasts by follistatin expression”. Biological & Pharmaceutical Bulletin. 36 (9): 1460–5. PMID 23995658.
3. Han X, Moller LLV, et al. Mechanisms involved in follistatin-induced hypertrophy and increased insulin action in skeletal muscle. J Cachexia Sarcopenia Muscle. 2019 Aug 11. doi: 10.1002/jcsm.12474
4. Castonguay R, Lachey J, Wallner S, et al. Follistatin-288-Fc Fusion Protein Promotes Localized Growth of Skeletal Muscle. J Pharmacol Exp Ther. 2019 Mar;368(3):435-445. doi: 10.1124/jpet.118.252304. Epub 2018 Dec 18.
5. Su Jin Lee, Amal Gharbi, Joo Eun Shin, In Duk Jung, Yeong Min Park, Myostatin inhibitor YK11 as a preventative health supplement for bacterial sepsis, Biochemical and Biophysical Research

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