S4 (Anadrine)

S4, also known as Andarine, is a selective androgen receptor modulator (SARM) with high affinity for androgen receptors in muscle and bone tissue. Originally developed by GTx Inc. for the treatment of muscle wasting and osteoporosis, S4 is widely used as a tool compound in androgen receptor research, body composition studies, and tissue-selective androgenic signaling investigation.

S4 SARM (Andarine) is a non-steroidal selective androgen receptor modulator (SARM) that was among the earliest SARMs developed for therapeutic research. Originally investigated by GTx Inc. as a potential treatment for conditions including muscle wasting, osteoporosis, and benign prostatic hyperplasia, S4 demonstrates selective activation of androgen receptors in muscle and bone tissue while exhibiting reduced activity in other androgen-responsive tissues.

As a SARM, S4 binds to androgen receptors with high affinity and produces tissue-selective anabolic effects. This selectivity profile makes it particularly valuable for studying androgen receptor mechanisms and understanding how structural modifications influence tissue-specific responses to androgenic compounds.

S4 Name and Classification

S4 is identified by multiple designations in scientific literature, including Andarine, S-4, and GTx-007.

S4 was originally developed by GTx Inc. as part of a broader program investigating non-steroidal SARMs for various androgen-related conditions. The compound's development pathway overlapped with other notable SARMs from the same research program.

Mechanism of Action

Like all SARMS, S4 functions by selectively binding to androgen receptors, particularly in muscle and bone tissue. This selective activation triggers anabolic processes in target tissues while demonstrating reduced androgenic activity in others such as prostate tissue.

Key mechanistic features include:

• High androgen receptor binding affinity with tissue-selective activation
• Partial agonist activity at the androgen receptor
• Preferential activity in skeletal muscle and bone
• Reduced prostate tissue stimulation compared to traditional androgens
• Non-aromatizing properties - does not convert to estrogen

In experimental models, S4 demonstrates the ability to stimulate muscle protein synthesis and increase bone mineral density while producing minimal androgenic effects in non-target tissues. The partial agonist profile distinguishes S4 from full agonist SARMs and contributes to its unique pharmacological characteristics.

Benefits in Research

In preclinical research settings, S4 has been studied for its effects on muscle, bone, and body composition. Published animal studies suggest that S4 may:

• Increase lean muscle mass through androgen receptor activation in skeletal muscle
• Enhance bone mineral density and bone strength
• Reduce body fat percentage through effects on metabolism and body composition
• Preserve muscle mass in castration and denervation models
• Demonstrate tissue-selective androgenic effects useful for studying AR biology

These findings from controlled experimental models help researchers understand tissue-selective androgen receptor activation and the potential for developing therapeutic agents that separate anabolic from androgenic effects.

S4 Dosage in Experimental Studies

Most available data on S4 dosage comes from controlled animal research. Published studies report varying protocols depending on species, research objectives, and endpoints measured.

Typical experimental dosing ranges:

• 3-10 mg/kg administered once daily in rodent models
• Low-dose protocols (3 mg/kg) for studying selective tissue effects
• Medium-dose protocols (10 mg/kg) for evaluating anabolic and bone-protective effects
• Dose-escalation studies to determine efficacy and safety thresholds

Dosing considerations in research:

• Oral administration is standard due to acceptable bioavailability
• Short half-life (approximately 4-6 hours) may require multiple daily doses in some protocols
• Duration of administration varies from acute studies to chronic protocols (several weeks)
• Higher doses produce more pronounced effects on muscle and bone parameters

The S4 dosage used in research directly impacts the degree of anabolic effects, tissue selectivity, and overall physiological response, making dose selection a critical component of experimental design. The relatively short half-life of S4 influences dosing frequency considerations in research protocols.

S4 Side Effects in Research Models

Because S4 is a selective androgen receptor modulator with partial agonist activity, S4 side effects observed in research depend on dosage, duration, and individual response characteristics. In animal models and limited human observations, researchers monitor for:

Visual effects:

• Yellow-tinted vision or color perception changes, particularly in low-light conditions
• Night vision impairment or difficulty with dark adaptation
• Transient visual disturbances that appear dose-dependent and reversible
• Hypothesized mechanism involves S4 binding to retinal receptors

Androgenic and hormonal effects:

• Mild testosterone suppression at higher doses, though less pronounced than stronger SARMs
• Changes in sex hormone levels with dose-dependent effects on LH and FSH
• Minimal prostate tissue effects due to tissue selectivity

Physical and metabolic observations:

• Altered lipid profiles including changes in HDL and LDL cholesterol
• Mild liver enzyme elevations in some subjects at higher doses
• Generally favorable tolerability compared to traditional androgens

Tissue-specific effects:

• Desired anabolic changes in muscle and bone tissue
• Body composition shifts reflecting androgenic activity
• Reduced androgenic effects in non-target tissues

The most notable and distinctive S4 side effect involves visual disturbances, which appear unique among SARMs and are hypothesized to result from S4's interaction with ocular receptors. These visual effects are typically dose-dependent and reversible upon discontinuation or dose reduction. Understanding these side effects helps researchers establish safe dosing parameters and characterize S4's full pharmacological profile in experimental settings.

S4 and Vision Research

One unique aspect of S4 research involves investigation of its visual side effects. The yellow-tinted vision and night vision impairment observed with S4 use has led to research examining the compound's interaction with retinal proteins and visual receptors. Studies suggest S4 may bind to receptors in the eye involved in dark adaptation and color perception, though the exact mechanism remains under investigation. This distinctive profile makes S4 valuable for studying selective receptor interactions beyond traditional androgen-responsive tissues.

Oral Administration in Research

S4 demonstrates acceptable oral bioavailability in animal studies, making oral administration the standard route in most experimental protocols. The relatively short half-life (4-6 hours) influences dosing frequency, with some research protocols employing twice-daily or even three-times-daily dosing to maintain more stable plasma concentrations.

This allows researchers to examine sustained effects on muscle, bone, and body composition while investigating the pharmacokinetic characteristics of short-acting SARMs.

Human Clinical Trials

S4 underwent early-phase human clinical trials for conditions including muscle wasting and benign prostatic hyperplasia. While preclinical results were promising, development was not advanced to late-stage trials. The compound did not progress to regulatory approval, and comprehensive human safety and efficacy data remains limited in published literature.

Current research continues at the preclinical level, with S4 serving as a tool compound for understanding androgen receptor biology and tissue-selective modulation.

Why You Should Buy S4 from Sarmful

If you are looking to buy S4 for research purposes, we offer S4 for sale in liquid or powder form, prepared to support consistent and reliable experimental work.

When you buy S4 from Sarmful, you benefit from:

• Third-party lab testing and in-house verification for purity and concentration
• EU and US domestic shipping for reliable delivery to your research facility
• Convenient payment methods designed for seamless research procurement
• Research-grade quality formulated to meet the standards of serious laboratory work