LGD-4033 and Pitavastatin Interaction: Avoid | Peptide Database

Join others researching YK-11 — share findings, ask questions, and learn from real experiences YK-11 is a steroidal compound that occupies a unique position among selective androgen receptor modulators (SARMs) due to its dual mechanism of action: it functions as both a partial agonist of the androgen receptor and an inhibitor of myostatin through upregulation of follistatin. First described by Kanno et al. in 2011, YK-11 was identified in cell-based assays as a compound that selectively activates androgen-responsive gene transcription while simultaneously inducing follistatin expression, a glycoprotein that binds and neutralizes myostatin, a negative regulator of muscle growth. Unlike all other commercially known SARMs, YK-11 possesses a steroidal backbone structurally related to dihydrotestosterone (DHT), making its classification as a traditional SARM debatable. It is more accurately described as a steroidal SARM hybrid with myostatin-inhibiting properties. The research base for YK-11 is extremely limited. All published data comes from in vitro (cell culture) studies only. There are no animal studies, no pharmacokinetic studies, and no human clinical trials. As a result, virtually everything reported about YK-11's effects in living organisms, its half-life, optimal dosing, and side effect profile, is derived from structural analogy to related compounds, theoretical pharmacology, and anecdotal user reports. YK-11 is not approved for any medical use and is classified as an investigational research chemical. YK-11 exerts its effects through two distinct but complementary pathways. First, it acts as a partial agonist of the androgen receptor (AR). In C2C12 myoblast cell culture studies, YK-11 induced androgen receptor-dependent gene transcription at levels comparable to DHT for certain target genes, but with partial rather than full agonist activity. This partial agonism may theoretically confer some degree of tissue selectivity, though this has never been demonstrated in vivo. Second, and more uniquely, YK-11 stimulates the expression of follistatin in muscle cells. Follistatin is an endogenous glycoprotein that binds and inhibits myostatin (GDF-8), a member of the TGF-beta superfamily that acts as a potent negative regulator of skeletal muscle mass. By increasing follistatin levels, YK-11 may effectively reduce myostatin signaling, thereby removing a biological brake on muscle hypertrophy. In the original Kanno et al. study, YK-11-treated C2C12 cells showed significantly greater follistatin expression than cells treated with DHT alone, and this effect was blocked by an androgen receptor antagonist, indicating the follistatin induction is AR-dependent. The 17-alpha alkylation of YK-11's steroidal structure provides oral bioavailability but also subjects it to hepatic first-pass metabolism, with the associated risk of liver stress characteristic of 17-alpha alkylated compounds. Due to the complete absence of in vivo pharmacokinetic data, the compound's actual bioavailability, distribution, metabolism, and elimination profile in living systems remain unknown.

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