S 23 (Mastorin) by Dragon Pharma
What Is S 23 (Mastorin)?
S 23, sold by Dragon Pharma under the name Mastorin, is a high-potency selective androgen receptor modulator (SARM) presented as 10 mg oral tablets with 100 tablets per pack. In early research it was studied as a tissue-selective androgen that builds on the androgen receptor in muscle and bone with fewer of the androgenic effects on skin and prostate that come with full steroids. Among SARM compounds it sits at the stronger end of the spectrum, closer in character to a mild anabolic than to a simple supplement.
Recomposition and conditioning are where S 23 gets the most attention in performance circles. The typical reports describe strength that holds up through a calorie deficit, a harder and drier look, and better muscle retention while body fat drops. It is a tablet, so there is no injection to prepare, but that convenience is balanced by one of the heaviest suppression profiles of any SARM: endogenous testosterone drops fast and hard at the doses researchers explore.
Dragon Pharma S 23 (Mastorin) 10 mg is aimed at advanced researchers who already understand suppression-aware protocols and full PCT planning. It is not a beginner compound, and it should be treated with the same respect as an injectable androgen rather than as an easy oral.
S 23 (Mastorin) Research Use
S 23 is dosed once per day in most research references, and the tablet form makes that simple: take the same time daily with or without food. Reference ranges for S 23 typically sit between 10 mg and 25 mg per day, with most protocols starting at the lower end to gauge tolerance before moving up.
| Parameter | Reference value | Note |
|---|---|---|
| Starting dose | 10 mg per day (one tablet) | Run the first week at the low end |
| Maintenance | 20-25 mg per day | Most commonly explored range |
| Frequency | Once daily | Consistent daily timing |
| Research window | 8-12 weeks | Longer runs deepen suppression and lipid shifts |
Bloodwork Guidance
Because S 23 suppresses natural testosterone strongly and quickly, a research protocol is incomplete without a PCT plan built in advance. Bloodwork before, midway and after the window is the standard way to track testosterone, lipids and liver values, and training should be paired with adequate calories and recovery to judge the compound fairly.
S 23 (Mastorin) Stacks
In performance research S 23 is usually run with a testosterone base or with metabolic and recovery partners rather than with another SARM. Every partner below belongs to the same Dragon Pharma line.
| Stack partner | Role in the stack |
|---|---|
| Enanthate 250 | Testosterone base that offsets S 23 suppression in longer protocols |
| Cypionat 250 | Alternative long-ester test base for the same role |
| MK 677 (Ibutamoren) | Appetite, sleep and recovery support during the deficit |
| GW 501516 | Endurance and conditioning partner for cardio-heavy blocks |
| Clomid | PCT anchor for the recovery phase after the S 23 window |
| Nolvadex | SERM alternative for post-protocol recovery |
Stacking two suppressive SARMs together is not recommended in reference practice, since it multiplies hormonal damage without a clear benefit. Keep S 23 as the single androgen signal or put a testosterone base underneath it, and plan the recovery phase before the first tablet.
S 23 (Mastorin) Side Effects
S 23 carries the risks of a potent SARM, and the two that dominate every research log are testosterone suppression and cholesterol changes. It should be approached with the planning of a steroid cycle, not the casualness of a supplement.
- Testosterone suppression: fast and strong; most protocols require a full PCT afterward
- Lipids: HDL cholesterol drops and LDL tends to rise during the run
- Lethargy and low energy: common as suppression deepens, especially without a test base
- Libido changes: usually follow the testosterone level, up early and down late in the run
S 23 (Mastorin) is a research chemical. It is not approved for human or veterinary use, and its long-term safety profile is unknown. Keep it away from food, drink and skin contact, and store it out of reach of children.
For research use only. Nothing on this page is medical advice, and no dosing recommendation here is intended for human consumption.
What is S-23?
S-23, sold by Dragon Pharma as Mastorin, is a selective androgen receptor modulator (SARM), not a steroid. It was developed for tissue-selective androgen effects and is used in research settings for strength and recomposition work.
Is S-23 a steroid?
No, S-23 is a SARM. It binds the androgen receptor like a steroid would but is designed to act more selectively in muscle and bone tissue. In practice it is potent enough that it behaves closer to a mild anabolic than to a supplement.
What is S-23 used for in bodybuilding?
Research interest centers on recomposition: holding onto strength and muscle while dieting, plus a harder, drier look. It is usually placed in cutting or recomp blocks rather than mass phases.
What is the recommended S-23 dosage?
Reference protocols commonly use 10-25 mg per day as a single dose. Most logs start at 10 mg for the first week and only move up if tolerance and bloodwork allow.
How long should an S-23 cycle last?
Most research windows run 8-12 weeks. Going longer increases suppression and cholesterol damage without proportionally better results, and recovery time gets longer the deeper the suppression goes.
Does S-23 suppress natural testosterone?
Yes, strongly and quickly. S-23 is considered one of the most suppressive SARMs, and most researchers plan a full PCT with a SERM after the window because natural levels do not bounce back on their own quickly.
Does S-23 require PCT?
Yes, a structured PCT is standard after an S-23 window. Clomid or Nolvadex are the usual recovery anchors, and bloodwork should confirm that testosterone has rebounded before ending the recovery phase.
What are the side effects of S-23?
The main effects are testosterone suppression, a drop in HDL cholesterol, lethargy as suppression deepens, and possible libido swings. Since S-23 is a research chemical, its long-term safety profile is not established.
Is S-23 FDA approved?
No. S-23 was investigated in preclinical research but has never been approved for medical use anywhere. Products sold as S-23, including this one, are for laboratory research only.
Where can I buy S-23 online?
S-23 Mastorin by Dragon Pharma is available from this shop as a 100-tablet pack of 10 mg tablets. Ordering from the official store page keeps you away from underdosed or mislabeled research chemical sources.
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