Description
S4 (Andarine) is a non-steroidal, oral selective androgen receptor modulator and one of the historically earliest representatives of the SARM class. The substance was developed by GTx, Inc. for the treatment of muscle-wasting diseases and osteoporosis, but was not advanced to late clinical phases because of visual tissue side effects.
Per study reports Andarine binds to the androgen receptor with moderate affinity and exerts tissue-specific agonistic effects. Studies in gonadectomized rats showed muscle and bone building effects, with better selectivity over prostate than classical steroids.
The best-known side effect in studies is yellowish visual tinting (yellow-tint vision): Andarine binds in the eye to a receptor in photoreceptors and impairs adaptation to low light. The effect is reversible after discontinuation but is consistently documented in many studies during research protocols. Visual-field sensitivity changes were also described in Phase I studies.
Pharmacokinetically Andarine is orally bioavailable with about a 4-hour half-life, requiring 2-3 daily doses. Compared to modern SARMs like LGD-4033 or RAD-140 this pharmacokinetic profile is practically problematic.
In the recreational community Andarine is increasingly being replaced by newer SARMs due to the visual side effect and short half-life. The compound remains relevant in literature as a reference for early SARM studies.
You can order Andarine as oral tablets in one bottle with 25mg per tablet.
This information is for research and educational purposes only. No medical recommendations.
Risks & Safety
Andarine sits in the mid range of the risk scale. As one of the earliest clinically-tested SARMs the compound has a characteristic, well-documented side effect.
Documented in studies and the literature:
- Yellowish visual disturbance: the documented yellow-tint vision effect - Andarine binds in the eye to a receptor in the photoreceptors and impairs adaptation to low light. Reversible after discontinuation, but consistently described during the protocol.
- HPG suppression: documented in moderate form, lower than under LGD-4033 but present.
- HDL suppression: a lowering of HDL cholesterol is documented as a class effect of SARMs.
- PCT requirement: because of the HPG suppression, a SERM PCT after longer cycles is customary in the literature.
Monitoring via bloodwork is recommended. This classification does not replace medical advice. Risk and responsibility for any actual use lie entirely with the buyer.
Studies
- Pharmacodynamics of Selective Androgen Receptor Modulators - The Journal of Pharmacology and Experimental Therapeutics 2003, Yin et al: preclinical characterization of S-1 and S-4, tissue-selective anabolic activity in castrated rats.
- Comparison of the Pharmacological Effects of a Novel Selective Androgen Receptor Modulator, the 5α-Reductase Inhibitor Finasteride, and the Antiandrogen Hydroxyflutamide in Intact Rats: New Approach for Benign Prostate Hyperplasia - Endocrinology 2004, Gao et al: S-4 preserves muscle mass while reducing prostate weight in intact rats.
- Selective Androgen Receptor Modulator (SARM) Treatment Prevents Bone Loss and Reduces Body Fat in Ovariectomized Rats - Pharmaceutical Research 2006, Kearbey et al: S-4 prevents bone loss and lowers body fat in an osteoporosis model.
- Selective Androgen Receptor Modulators: Current Knowledge and Clinical Applications - Sexual Medicine Reviews 2019, Solomon et al: review with Andarine in the historical context of the SARM class.
