S 23 (Mastorin) - Dragon Pharma

Buy S 23 10 mg tablets by Dragon Pharma at XSteroids. S-23, also called Mastorin, is one of the most potent selective androgen receptor modulators ever described - and the one that was designed as a male contraceptive rather than as a muscle drug. Dragon Pharma supplies it as 10 mg tablets, 100 per pack. This guide covers what the research shows, what is missing from it and how s23 dosage is handled in practice.

S-23 is an Investigational New Drug and has never been approved for any use, so the information below is educational only.

About S 23 (Mastorin) by Dragon Pharma

S-23 was developed by GTx as a potential male hormonal contraceptive. The logic is straightforward: if a compound can suppress sperm production reliably and reversibly, it can work as birth control for men - and the same pharmacology makes it interesting to people chasing lean mass.

Its binding profile is the headline number. S-23 binds the androgen receptor more strongly than older SARMs such as andarine, with a Ki of 1.7 nM, which places it among the most potent compounds in the class. It appears in non-medical circulation as a designer drug.

How S-23 Works

Receptor Binding and Animal Data

In animal studies, S-23 showed both a favourable ratio of anabolic to androgenic effects and a dose-dependent suppression of spermatogenesis, with spontaneous recovery of fertility after treatment stopped. That combination - strong anabolic signalling plus reversible shutdown of sperm production - is exactly what a male contraceptive needs, and it is also what makes the compound so suppressive for anyone using it.

What the Human Data Does Not Cover

This is worth stating plainly: S-23 has no published human dosing, no human pharmacokinetic profile and no human safety dataset. Unlike Ostarine, which has 25 clinical trials behind it, S-23 remains almost entirely preclinical. Anything said about its half-life in humans is extrapolation, which is why this card lists it as not established.

S23 Dosage and Cycle Practice

Dosing in Practice

With no human dose established, non-medical use is guesswork: published product practice centres on 10 mg per day, and the tablet strength here matches that. Because the compound is potent at the receptor and clearly suppresses the gonadal axis, the sensible approach is to start low, keep the cycle short and track blood work - not to escalate.

Suppression and Recovery

S-23 suppressed spermatogenesis in animals, which means it acts on the hypothalamus-pituitary-gonadal axis hard. In humans, a SARM with that profile is expected to suppress testosterone too, and recovery has to be planned rather than assumed. A SERM such as Nolvadex or Clomid is the standard recovery tool, with LH, FSH and total testosterone checked afterwards.

S-23 Side Effects and What to Watch

Because the human evidence is essentially absent, side effects cannot be listed with the certainty that applies to LGD 4033 or Ostarine. The class-level picture applies: suppressed natural testosterone and fertility during use, changes in lipids, and possible liver enzyme elevation. Anyone using a compound with reversible contraceptive pharmacology should assume fertility effects until blood work and, if relevant, semen analysis say otherwise.

How S-23 Compares to Other SARMs

Ostarine is the mildest and most studied; LGD 4033 is stronger with trial data behind it; S-23 is more potent still at the receptor and much less documented. YK 11 sits in a different experimental corner of the class, while MK 677 is not a SARM at all - it works through the ghrelin receptor - and GW 501516 is a metabolic research compound rather than an androgen receptor agonist.

Storage Instructions

Store the tablets at room temperature in a dry place, away from direct light and moisture. Keep the pack sealed until use and always store it out of the reach of children.

Why Buy S 23 from XSteroids?

At XSteroids you buy the Dragon Pharma S 23 tablets directly from the brand catalog, with secure checkout, US domestic shipping in 3 to 6 days and international delivery in 12 to 26 days. Browse the full range on the Dragon Pharma brand page to complete your research protocol.