Description
YK11 is a synthetic steroid derivative with unusual pharmacology. Structurally YK11 is based on a 5α-DHT scaffold with additional cyclopropane modification; mechanistically the substance is often categorized as a “SARM” but is a partial androgen receptor agonist with a second action pathway via follistatin/myostatin modulation.
Per study reports YK11 in the original Kanno et al 2011 study (Biological and Pharmaceutical Bulletin) increased follistatin expression in C2C12 muscle cells. Follistatin is a natural myostatin antagonist, so YK11 indirectly releases the myostatin brake on muscle growth. This mechanism is distinct from classical AR agonists.
The data on YK11 is substantially thinner than for other SARMs. There are only a handful of preclinical studies, no clinical studies, and no complete pharmacokinetic data in human models. What is known: orally available, presumed half-life of about 6-10 hours based on recreational research reports.
Because of the steroid structure YK11 is often positioned by the recreational community as a “hybrid” between classical anabolic and SARM. Hepatotoxicity due to the 17α-methyl-like modification is more frequent in practical reports than with non-steroidal SARMs like LGD-4033.
YK11 is on the WADA banned list.
You can order YK11 as oral tablets in one bottle with 10mg per tablet.
This information is for research and educational purposes only. No medical recommendations.
Risks & Safety
YK11 sits in the mid range of the risk scale, with one important caveat: the data situation is substantially thinner than for other compounds in this class.
Documented in studies and the literature:
- Very thin data situation: there are only a handful of preclinical studies, no clinical studies, and no complete pharmacokinetic data in human models.
- Hepatotoxicity: because of the steroid structure with 17-alpha-methyl-like modification, a liver marker elevation is more frequent in practical reports than with non-steroidal SARMs.
- HPG suppression: as a partial AR agonist YK11 suppresses the HPG axis, and a SERM PCT after the cycle is customary in the literature.
- Unclear long-term safety: because of the missing study base, the long-term profile remains largely uncharacterized.
Monitoring via bloodwork is recommended. This classification does not replace medical advice. Risk and responsibility for any actual use lie entirely with the buyer.
Studies
- (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 and Pharmaceutical Bulletin 2011, Kanno et al: original characterization of YK11 as a partial androgen receptor agonist.
- Selective Androgen Receptor Modulator, YK11, Regulates Myogenic Differentiation of C2C12 Myoblasts by Follistatin Expression - Biological and Pharmaceutical Bulletin 2013, Kanno et al: YK11 increases follistatin expression and drives myogenic differentiation in C2C12 muscle cells.
- Selective Androgen Receptor Modulator, YK11, Up-Regulates Osteoblastic Proliferation and Differentiation in MC3T3-E1 Cells - Biological and Pharmaceutical Bulletin 2018, Yatsu et al: YK11 promotes proliferation and differentiation of osteoblast cells.
- Selective Androgen Receptor Modulators: Current Knowledge and Clinical Applications - Sexual Medicine Reviews 2019, Solomon et al: review of the SARM class including YK11.
