• This drug was initially developed as a male contraceptive.
  • It is a potent Androgen Receptor agonist (helps activates the receptor) and very selective meaning it binds to bone and muscle, and no other unwanted tissues.
  • Studies of S-23 in humans are lacking however there are in vitro (‘Test Tube’) and in vivo (animal studies) studies.
  • In the studies, oestradiol (exogenous oestrogen) has to be given to the animals in order to maintain normal sexual function since S-23.
  • In a study conducted on rats, S-23 resulted in fat loss and muscle gain. Furthermore, prostate size decreased (a positive).
  • S-23 was noted, however, to be a potent suppressor of natural testosterone and spermatogenesis (making sperm cells) essentially rendering 100% of subjects infertile. However, fertility was seen to be re-established after discontinuation of S-23.
  • Higher doses of S-23 had a surprising effect. The rats receiving high doses of S-23 became fertile.
  • Very few studies have been conducted.

Side Effects:

  • Little is known about this SARM.
  • We must extrapolate data on rats to come to any conclusions.
  • S-23 potently supresses testosterone. Therefore, it should not be used by itself since symptoms of low testosterone may appear. Therefore, it should ideally be used with a testosterone base and a PCT (Post-cycle therapy) is required.
  • ‘Roid rage’ has been often reported by individuals using this drug, some reporting it to be the worse than other more well-known anabolic agents.
  • Hair loss has been reported.
  • It suppresses oestrogen levels (most likely through decreasing testosterone which converts to oestrogen). Therefore, this further supports the need for a testosterone base in your cycle or exogenous oestrogen.
  • It’s toxicity to the liver is unknown at this point.


  • The half life is approximately 12 hours which means twice a day dosing should be used.
  • It is taken at doses ranging from 10 to 30 mg a day divided into two doses.
  • S-23 is reported to be useful in individuals looking to attain a leaner physique or ‘ripped’ physique whilst maintaining muscle mass.
  • Cycles should not exceed 8 weeks.

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