Ligandrol (LGD-4033), CAS number 1165910-22-4 is a selective androgen receptor modulator that is more potent per milligram dose, less selective and even less researched than ostarine, the most well-researched SARM. Only one study [1] has been related to investigation of its biological effects, while most of the research effort has been aimed towards doping detection instead. Despite all but minimal research, it has been used as a doping substance. One milligram dose of ligandrol suppressed total testosterone and sex hormone binding globulin, HDL cholesterol and triglycerides as well as free testosterone and FSH (follicle stimulating hormone) indicating that 1 mg dose was sufficient to cause some probably unwanted side effects associated with androgenc mechanism of action in addition to the sought after effect, which was increased muscle mass [1]. However, no serious adverse effects or increased liver enzymes were not detected, and both probably unwanted reduced hormone levels as well as probably desirable reduced lipid levels returned to baseline after discontinuation of ligandrol.

References:

[1] https://www.ncbi.nlm.nih.gov/pubmed/22459616