Selective Androgen Receptor Modulators (SARMs) represent one of the most actively researched compound classes in endocrinology and musculoskeletal biology. Designed to engage the androgen receptor (AR) with tissue-selective profiles, SARMs aim to provide anabolic effects in muscle and bone while minimizing activity in prostate and sebaceous tissue.

All SARMs discussed are research compounds for in-vitro laboratory use only. Not for human consumption.

Understanding Androgen Receptor Selectivity

SARMs achieve tissue selectivity by altering helix-12 of the AR ligand-binding domain. Different conformational states recruit different coactivator proteins, producing cell-type-specific transcriptional programs -- the mechanistic basis for tissue selectivity (Narayanan et al., 2008).

Ostarine (MK-2866): The Most Studied SARM

Ostarine (MK-2866) is the most extensively characterized SARM in the clinical literature. A non-steroidal partial AR agonist, it preferentially activates anabolic gene programs in skeletal muscle and bone.

Key Research Findings

  • Phase 2 trials in cancer-related muscle wasting showed statistically significant lean body mass gains vs placebo (Dalton et al., 2013).
  • Ovariectomy-induced osteoporosis models demonstrate Ostarine preservation of bone mineral density.
  • Dose-dependent LH and testosterone suppression documented at higher doses -- relevant for HPG axis research.

Ligandrol (LGD-4033): High-Affinity Muscle Research

Ligandrol (LGD-4033) is a full AR agonist with one of the highest binding affinities among non-steroidal SARMs. Phase 1 study showed lean body mass gains of 1.21 kg in 21 days at 1 mg/day with benign PSA profile. Viking Therapeutics Phase 2 (VK5211) in hip fracture patients showed significant improvements in lean body mass, functional tests, and bone density.

Testolone (RAD-140): Anabolic and Neuroprotection Research

Testolone (RAD-140) demonstrates greater anabolic potency per mg than testosterone propionate in muscle with significantly less prostate weight increase. Uniquely, RAD-140 activates AR in neurons and has shown protective effects against amyloid-beta toxicity and kainate-induced neurotoxicity -- positioning it distinctively in neurological research alongside its muscle biology applications.

Cardarine (GW-501516): PPARdelta Agonist

Cardarine (GW-501516) is a PPARdelta agonist -- not an AR ligand. PPARdelta regulates fatty acid oxidation in skeletal muscle, stimulates mitochondrial biogenesis, and promotes the metabolic shift toward lipid utilization. Key research: dramatic endurance increases in rodent models through fatty acid oxidation gene upregulation, and HDL elevation with LDL/triglyceride reduction in primate studies.

Ibutamoren (MK-677): Oral GH Secretagogue

Ibutamoren (MK-677) is a ghrelin receptor (GHSR-1a) agonist -- the only GH secretagogue available in oral form for research. Applications span GH/IGF-1 axis biology, muscle catabolism prevention, sleep architecture, cognitive aging, and bone density studies.

S-23, YK-11, and SR-9009: Advanced Research Compounds

  • S-23 -- Full non-steroidal AR agonist with highest binding affinity among available SARMs. Also studied for male contraceptive potential.
  • YK-11 -- Partial AR agonist that also inhibits myostatin (GDF-8). Dual mechanism makes it distinctive in muscle biology research.
  • SR-9009 (Stenabolic) -- Rev-Erb agonist affecting circadian rhythm regulation and metabolic gene expression in liver, fat, and muscle.

Research Design Considerations

  • HPG axis effects -- All AR agonist SARMs suppress LH and testosterone in intact male models. Account for endogenous androgen suppression in experimental design.
  • Tissue selectivity validation -- Claimed selectivity profiles should be empirically validated in your specific model system.

Explore the full SARMs research collection at PeptideBull -- all compounds HPLC-verified at 99%+ purity with COA documentation.

Disclaimer: All products are for in-vitro research use only. Not for human consumption.