What is S-4?
As a research chemical, S-4 belongs to a class of chemicals known as SARMS or selective androgen receptor modulators. Like typical androgens, SARMS bind to the androgen receptor however SARMS create selective anabolic activity.
Compared to testosterone and other anabolic steroids and pro hormones, the advantage of SARMS such as S-4 is that they do not have androgenic activity in non-skeletal-muscle tissues.
S4 was designed for treatment of conditions such as muscle wasting, osteoporosis and benign prostatic hypertrophy, using the non-steroidal androgen antagonist bicalutamide as a lead compound.
As an orally active partial agonist for androgen receptors, S-4 is effective in not only maintaining lean body mass but actually increasing it.
How does it work?
Selective androgen receptor modulators (SARMS) bind to the androgen receptor and demonstrate osteo (bone) and myo (muscular) anabolic activity.
Binding and activation of the Androgen receptor alters the expression of genes and increases protein synthesis which ultimately builds muscle.
SARMS such as S4 can cause muscle growth in the same manner as steroids, however unlike testosterone and other anabolic steroids, SARMS (as nonsteroidal agents) do not produce the growth effect on prostate and other secondary sexual organs.
SARMS not only represent a new potential treatment option for a wide spectrum of conditions such as muscle wasting diseases (from age-related to AIDS or cancer-related), but they also have immense potential for muscle building for Bodybuilders, fitness and athletes.
S-4 in particular binds to the androgen receptor in muscle and bone to a third of the affinity of Testosterone.
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Evidence of S-4 Abilities?
S-4 (3 mg/kg/day) was also able to restore skeletal muscle (i.e., soleus muscle) and strength in castrated rats, important and applicable for the treatment of muscle wasting and male HRT.
A 120-day study comparing SARM S-4 and dihydrotestosterone (DHT) treatment in ovariectomized rats demonstrated that S-4 was able to maintain bone mass and bone strength to the levels of intact controls and exhibited greater efficacy than DHT.
S-4 also demonstrated the ability to improve skeletal (soleus) muscle strength, increase lean body mass, reduce body fat, and prevent bone loss.
Uses of S-4:
Losing Bodyfat (Cutting)
Cutting is the environment where S-4 truly shines.
Certain steroids are considered “cutting” steroids such as Winstrol and Anavar. These steroids don’t offer too much in large gains in muscle mass but are very effective in leaning out the body. The SARM S-4 has very similar properties.
The presence of androgen receptors in human preadipocytes and adipocytes suggests that androgens may contribute, through regulation of their own receptors, to the control of adipose tissue development. As S-4 shows this binding affinity to the AR, it demonstrates the similar fat burning effects. S-4 also shows a decrease in LPL (lipoprotein lipase) which is an enzyme that causes lipid accumulation.
S-4 also fits into a cutting protocol for the concurrent reduction in body fat with maintenance of muscle mass in a hypocaloric environment.
One of the most disheartening outcomes of cutting is the loss hard earned muscle mass. The drop in metabolic rate and hormone levels (T3, IGF, Testosterone etc) with the lack of calories is a perfect catabolic environment for loss of muscle tissue.
As S4 has both anabolic and androgenic effects in muscle tissue, it will not only help with fat loss, but maintain and even increase muscle mass when cutting.
S-4 causes increases in vascularity and promote a very nice, “quality”, hard look to the users muscles, with little or no water retention.
In this way S-4 can be compared to Winstrol, without the harsh hair loss or extreme adverse effects on cholesterol.
Also other popular steroids/Prohormones used for cutting such as winstrol or epistane can have a notable effect on drying out of the joints. S-4 doesn’t suffer such consequences so the athlete is still able to lift heavy in order to maintain/increase muscle mass and strength.
Another advantage S-4 offers for cutting is that it doesn’t give the painful pumps associated with other popular steroids/Prohormones. Back and calf pumps are particularly detrimental for cutting as it limits the ability to perform cardio.
S-4 Dosing for cutting
A 50mg dosing protocol for 6-8 weeks is ideal for cutting purposes for the majority of users.
However due to the vision side effects, if running at these doses some like to follow a 5 on 2 off protocol where S4 is used for 5 days followed by a 2 day break (then this cycle is repeated).
The recomping effect of losing fat and gaining muscle at the same time is what the majority of users are looking for. Trying to achieve this when you are not absolutely new to training is extremely difficult.
One of the most important factors of recomping is time. As you are trying to achieve multiple objectives, it requires a longer time period to notice good recomp effects so even when running steroids, these would have to be longer run injectable compounds as oppose to the short run liver toxic oral steroids.
Although S-4 is taken orally, it is not methylated and is not liver toxic like other AAS/PH/DS’s. As it prevents this side effect and many others, it can be ran for 6+weeks, sufficient time to get a good body recomp.
A dosing protocol of 50-75mg for 4-8 weeks will give good recomp effects
Diet must also be optimized to where calories are just above maintenance with at least 30% coming from lean sources of protein to get the best recomp effect.
Of course, the recomp effects could be even greater if stacked or combined with a more anabolic SARM such as Ostarine.
Strength gains and Lean mass gains
Due to its androgenicity in muscle tissue, S-4 is a good agent for increases in strength without bloat and large increases in weight.
Dosing at 50mg+ is the sweet spot for such gains.
Also due to its anabolic nature, these strength gains will come with associated gains in lean mass, albeit smaller than other more anabolic SARMS such as Ostarine.
Also, like the oral steroid Anavar (Var) weight gain with S4 may not be that great in comparison to bulking steroids such as deca or Superdrol, but what the lean mass and strength gained during the cycle is kept and not lost after the cycle.
With all dosing protocols, as the half life of S-4 is 4 hours, splitting up the dose into multiple applications is advised.
Also due to this short half life, users have found that taking one of these doses pre WO will offer increased performance in the gym.
S-4 and estrogen concern
SARMS cannot be aromatized, conferring all their effects to AR binding and not to metabolic conversion to active androgens/estrogens.
Unlike Ostarine where blood work from users has shown a slight elevation in serum estradiol levels, S-4 does not show any such elevation. As it has slight androgenic activity, it in fact gives the opposite effects and reduces bloat and other estrogenic effects. This is evident with the aforementioned hardening effects that S4 gives.
Advantages Of S4 when compared to Steroids/Prohormones
It is non methylated so it is not toxic to the liver or blood pressure
Some suppression may be present at doses of 50mg+ run for longer than 4 weeks, however a full PCT of prescription SERMs like nolva or clomid is not necessary.
Great sense of well being while on, (without the aggression which can often detrimentally impact users daily lives).
No need for a long time period off between cycles; the recommended time of period for normal steroid cycles would be Time on + PCT, so for a typical 6 week cycle and 4 week PCT, a user would have to wait another 10 weeks after PCT to start another cycle where SARMS recovery requires minimal rest in between.
Side effects of S4
Although S-4 negates the side effects listed above, there is one very unique side effect that comes with its use.
When run at the 50mg+ doses, many users report vision disturbances. Now these are only present when using S-4 and quickly disappear when S-4 use is discontinued.
The side effects are caused by the M1 metabolite and include night-time blindness and a slight yellowish tint to the vision for some users.
Although these side effects are temporary, if they are still a concern, as suggested earlier, a 5 on 2 off protocol where S-4 is used for 5 days followed by a 2 day break (then this cycle is repeated) would be the suggested dosing method.
- 1/3 as androgenic as testosterone in muscle tissue.
- Anabolic at doses above 50mg
- Great for strength
- Great for muscle hardness
- Great for enhanced vascularity
- Great for endurance (aerobic or anaerobic)
- Accelerated fat loss above 50mg
- Joint healing effects
- Half life of 4 hours
- Enhanced UHPLC-MS/MS screening of selective androgen receptor modulators following urine hydrolysis
- Detection of the arylpropionamide-derived selective androgen receptor modulator (SARM) S-4 (Andarine) in a black-market product
- SARM-S4 and metabolites detection in sports drug testing: a case report
- Detection of the selective androgen receptor modulator andarine (S-4) in a routine equine blood doping control sample
- Investigation of the selective androgen receptor modulators S1, S4 and S22 and their metabolites in equine plasma using high-resolution mass spectrometry
- Selective Androgen Receptor Modulator Treatment Improves Muscle Strength and Body Composition and Prevents Bone Loss in Orchidectomized Rats
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What would a PCT look like if taken alone, or with Ostarine?