Written by: FitScience Editorial Team
Medically Reviewed by: Dr Shalender Bhasin MD Last Updated: March 27, 2026
Disclaimer: FitScience.co provides this information strictly for educational, clinical reference, and harm-reduction purposes. Selective Androgen Receptor Modulators (SARMs) are investigational new drugs and are not approved by the FDA for human consumption. We do not condone or endorse the use of illegal or unapproved substances. Always consult a licensed endocrinologist or medical professional.
TL;DR Summary: Key Takeaways
- Most Clinically Researched: Ostarine (MK-2866) has the highest volume of human clinical trials, primarily for muscle wasting and cachexia.
- Highest Anabolic Affinity: RAD-140 (Testolone) and LGD-4033 (Ligandrol) display the highest binding affinity to androgen receptors for lean tissue accretion.
- Half-Life Variance: Terminal half-lives range dramatically, from approximately 4-6 hours (Andarine) to 60 hours (RAD-140), dictating whether compounds require multiple daily doses or single daily dosing.
- Suppression Reality: Clinical data confirms that all true SARMs cause dose-dependent suppression of the Hypothalamic-Pituitary-Testicular Axis (HPTA). Proper Post Cycle Therapy (PCT) protocols are a standard requirement in clinical and anecdotal literature.
- Non-SARM Classifications: Compounds frequently grouped with SARMs, such as Cardarine (GW-501516), Stenabolic (SR9009), and Ibutamoren (MK-677), operate on entirely different biological pathways (PPARδ, Rev-ErbA, and Ghrelin receptors, respectively) and do not suppress natural testosterone.
The Master SARMs & Associated Compounds Data Table
| Compound | Nomenclature | Primary Target / Class | Terminal Half-Life | Standard Research Dosage | HPTA Suppression Risk |
| Ostarine | MK-2866 / Enobosarm | SARM | ~24 Hours | 10mg – 25mg / day | Low to Moderate |
| Ligandrol | LGD-4033 / VK5211 | SARM | ~24 – 36 Hours | 5mg – 10mg / day | High |
| Testolone | RAD-140 | SARM | ~60 Hours | 10mg – 20mg / day | Very High |
| Andarine | S-4 | SARM | ~4 – 6 Hours | 25mg – 50mg / day | Moderate |
| S-23 | S-23 | SARM | ~11.9 Hours | 10mg – 20mg / day | Complete / Severe |
| YK-11 | YK-11 | SARM / Myostatin Inhibitor | ~12 Hours | 5mg – 10mg / day | High |
| LGD-3303 | LGD-3303 | SARM | ~6 Hours | 10mg – 20mg / day | High |
| ACP-105 | ACP-105 | SARM | ~4 – 6 Hours | 10mg – 15mg / day | Moderate |
| AC-262 | AC-262,536 | SARM | ~4 – 6 Hours | 10mg – 20mg / day | Low |
| RAD-150 | TLB-150 Benzoate | SARM | ~48 – 72 Hours | 5mg – 10mg / day | Very High |
| OTR-AC | Ostarine O-Acetate | SARM | ~24 Hours | 10mg – 20mg / day | Moderate |
| Cardarine | GW-501516 | PPARδ Receptor Agonist | ~16 – 24 Hours | 10mg – 20mg / day | None |
| Ibutamoren | MK-677 | Growth Hormone Secretagogue | ~24 Hours | 10mg – 25mg / day | None |
| Stenabolic | SR9009 | Rev-ErbA Ligand | ~4 Hours | 20mg – 30mg / day | None |
| Stenabolic | SR9011 | Rev-ErbA Ligand | ~4 Hours | 20mg – 30mg / day | None |
Clinical Breakdowns and Dosage Profiles
What is the Half-Life and Dosage of Ostarine (MK-2866)?
Ostarine (MK-2866) has a terminal half-life of approximately 24 hours, allowing for once-daily dosing. Standard clinical research dosages range from 1mg to 3mg, while sports-enhancement literature typically notes dosages between 10mg and 25mg per day.
Ostarine is the most extensively studied SARM, initially developed by GTx, Inc. to combat muscle wasting and osteoporosis. Because of its 24-hour half-life, stable blood serum levels are maintained with a single dose. While often categorized as a mild compound, clinical trials demonstrate that even a 3mg daily dose significantly lowers Sex Hormone-Binding Globulin (SHBG) and total testosterone levels after 21 days of continuous use.
RAD-140 (Testolone) vs. LGD-4033: Which is More Suppressive?
Both compounds are highly suppressive to endogenous testosterone production, but RAD-140 is clinically observed to have a harsher impact on the HPTA and lipid profiles compared to LGD-4033 at equivalent tissue-building dosages.
RAD-140, originally developed by Radius Health, has a much longer terminal half-life than previously documented in early literature, extending up to 60 hours. Daily dosing leads to rapid compound accumulation in blood serum, driving heavy suppression. LGD-4033, developed by Ligand Pharmaceuticals, demonstrated in phase 1 clinical trials that a dosage of just 1mg per day caused a robust suppression of total testosterone from baseline over 21 days, though recovery times were generally faster than those associated with RAD-140.
Is YK-11 a True SARM or a Steroid?
YK-11 is structurally a synthetic steroid derivative that acts as a partial agonist at the androgen receptor, but it is unique because it also functions as a myostatin inhibitor by inducing the expression of follistatin.
Because its chemical backbone closely resembles dihydrotestosterone (DHT), its classification is heavily debated in clinical circles. It carries a half-life of roughly 12 hours, typically requiring split daily dosing. Due to its steroidal structure, YK-11 is highly suppressive to natural testosterone production and carries a higher risk of hepatic (liver) toxicity compared to traditional non-steroidal SARMs like Ostarine.
Do MK-677 (Ibutamoren) and Cardarine (GW-501516) Require PCT?
No. Neither MK-677 nor Cardarine act on the androgen receptors, meaning they do not suppress natural testosterone production and do not require Post Cycle Therapy (PCT).
Although frequently sold and grouped with SARMs, they operate on entirely different biological pathways. MK-677 is an orally active growth hormone secretagogue that mimics the action of ghrelin, stimulating the pituitary gland to release growth hormone and IGF-1. Cardarine is a PPARδ receptor agonist originally developed to treat metabolic and cardiovascular diseases, significantly enhancing lipid oxidation and cardiovascular endurance without impacting the endocrine system.
What is the Most Suppressive SARM?
S-23 is widely considered the most suppressive SARM currently researched, originally developed by GTX, Inc. as a potential male hormonal contraceptive.
S-23 possesses an extremely high binding affinity to androgen receptors. In preclinical models, it demonstrated the ability to completely suppress spermatogenesis and luteinizing hormone (LH) to undetectable levels. With a half-life of approximately 11.9 hours, it requires split dosing. A rigorous PCT protocol is absolutely mandatory following any research application of S-23.
Clinical References & Outbound Sources
Murphy, M. G., et al. (1998). Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women. The Journal of Clinical Endocrinology & Metabolism.
Dalton, J. T., et al. (2011). The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. Journal of Cachexia, Sarcopenia and Muscle.
Miller, C. P., et al. (2011). Design, Synthesis, and Preclinical Characterization of the Selective Androgen Receptor Modulator (SARM) RAD140. ACS Medicinal Chemistry Letters.
Basaria, S., et al. (2013). The Safety, Pharmacokinetics, and Effects of LGD-4033, a Novel Nonsteroidal Oral, Selective Androgen Receptor Modulator, in Healthy Young Men. The Journals of Gerontology: Series A.
Kanno, Y., et al. (2013). The selective androgen receptor modulator YK11 regulates myogenic differentiation of C2C12 myoblasts by follistatin expression. Biological and Pharmaceutical Bulletin.