YK-11

YK-11, also known by its aliases Myostatin SARM or Myostatin-inhibiting SARM, is a synthetic investigative compound classified as a selective androgen receptor modulator (SARM). Despite sharing some structural similarities with steroids due to its steroidal backbone, YK-11 is typically categorized within the SARM class due to its proposed mechanism of action involving selective androgen receptor (AR) agonism. However, its unique characteristic lies in its additional proposed role as a myostatin inhibitor, which differentiates it from many other SARMs that primarily focus on AR modulation. Myostatin is a protein that naturally limits muscle growth; by potentially inhibiting this protein, YK-11 is hypothesized to allow for increased muscle development beyond natural genetic limits. Research on YK-11 has primarily been conducted in cellular and animal models, with human data remaining very limited. Most current understanding is derived from in vitro studies, which have shown YK-11's ability to act as a partial agonist of the androgen receptor and its potential to increase follistatin expression, a protein that directly inhibits myostatin. The compound is not approved for human use by regulatory bodies like the FDA and is considered a research chemical. Due to the lack of comprehensive clinical trials, its full efficacy, safety profile, and long-term effects in humans are not well established. Individuals interested in this compound should be aware of its unapproved status and the significant gaps in scientific knowledge regarding its use.