Masteron
Also known as: Mast, Drostanolone, Drostanolone Propionate, Drostanolone Enanthate, Mast P, Mast E
DHT-Derived Anabolic Steroid | Hardening & Anti-Estrogenic
Overview
Masteron (drostanolone) is a synthetic dihydrotestosterone (DHT)-derived anabolic-androgenic steroid originally developed and marketed as Masteril and Drostanolone Propionate for the treatment of inoperable breast cancer in postmenopausal women. It received FDA approval for this indication in the 1970s but has since been discontinued from pharmaceutical markets. Structurally, drostanolone is DHT with a 2-alpha-methyl group, which increases its anabolic potency and protects it from metabolic breakdown by 3-alpha-hydroxysteroid dehydrogenase in muscle tissue. As a DHT derivative, Masteron does not aromatize to estrogen and exhibits mild anti-estrogenic properties, likely through competitive inhibition at the aromatase enzyme or direct antagonism at the estrogen receptor. This makes it uniquely suited for cutting and contest preparation cycles where a dry, hard, and grainy physique is desired. Masteron is not a mass-building compound; its primary value lies in aesthetic enhancement, estrogen management, and synergy with other anabolic agents. It is available in two ester forms: the short-acting propionate (original pharmaceutical form) and the longer-acting enanthate (underground lab formulation). Effective results are most visible at lower body fat percentages, typically below 12-15%, where its hardening and drying effects become pronounced.
Key benefits
- Produces a hard, dry, and grainy appearance by eliminating subcutaneous water retention
- Mild anti-estrogenic properties that can reduce or replace the need for aromatase inhibitors on cycle
- Does not aromatize, eliminating estrogen-mediated side effects from the compound itself
- Enhances the visual effects of other steroids in a stack by reducing water retention and bloat
- Modest increases in strength without significant weight gain, useful for weight-class athletes
- Improves muscle density and vascularity at low body fat percentages
- Well-tolerated with a relatively mild side effect profile compared to other anabolic steroids
- Short detection window with propionate ester compared to many other injectable steroids
Mechanism of action
Drostanolone binds to the androgen receptor with high affinity, promoting protein synthesis and nitrogen retention in skeletal muscle. As a DHT derivative, it cannot be converted to estrogen by the aromatase enzyme, eliminating estrogen-related side effects such as water retention and gynecomastia from the compound itself. Masteron exhibits anti-estrogenic activity through a dual mechanism: it competitively inhibits aromatase enzyme activity (reducing conversion of other aromatizable steroids like testosterone to estradiol) and may act as a weak antagonist at estrogen receptors in breast tissue, which was the basis for its historical use in breast cancer treatment. This anti-estrogenic property is the reason Masteron can reduce or eliminate the need for dedicated aromatase inhibitors when stacked with testosterone. Unlike testosterone, drostanolone is not a substrate for 5-alpha reductase, as it is already a DHT derivative and cannot be further reduced. This means its full androgenic potency is expressed in all tissues, including hair follicles and the prostate, which accounts for its significant hair loss potential in genetically predisposed individuals. The 2-alpha-methyl modification prevents inactivation by 3-alpha-hydroxysteroid dehydrogenase in muscle, allowing drostanolone to exert its full anabolic effect at the tissue level rather than being rapidly metabolized to inactive forms as unmodified DHT would be.
Molecular data
- Type
- DHT-derived anabolic steroid (C20H32O2)
- Half-life
- ~2 days (propionate), ~10 days (enanthate)
Indications
What the research community uses this compound for, with self-reported effectiveness.
Oncology (Historical)
Inoperable Breast Cancer in Postmenopausal Women
ModerateDrostanolone propionate was FDA-approved for the treatment of advanced, inoperable breast cancer in postmenopausal women. Its anti-estrogenic properties provided tumor-suppressive effects in hormone-receptor-positive breast cancers. This indication has been superseded by modern selective estrogen receptor modulators and aromatase inhibitors, and pharmaceutical production has been discontinued.
Body Composition
Cutting and Contest Preparation
EffectiveMasteron is primarily used during cutting phases and pre-contest preparation to achieve a hard, dry, and defined physique. Its anti-estrogenic and non-aromatizing properties eliminate water retention from the compound, while its androgenic effects promote muscle hardness and vascularity. Most effective when body fat is below 12-15%.
Recomposition and Aesthetic Enhancement
ModerateAt moderate doses alongside a testosterone base, Masteron can improve body composition by promoting a leaner, more vascular appearance without significant scale weight changes. Commonly used in recomposition phases where the goal is visual improvement rather than mass gain.
Hormonal Management
Estrogen Control on Cycle
ModerateMasteron's mild anti-estrogenic properties allow it to reduce circulating estradiol levels when stacked with aromatizable compounds like testosterone. Some users employ it specifically to minimize or eliminate the need for pharmaceutical aromatase inhibitors, which can negatively impact lipids, joint comfort, and bone mineral density.
Dosing protocols
Common protocols by delivery method. Adjust the curve below to model accumulation in your own cycle.
Injectable
Masteron is administered exclusively via intramuscular injection. Two ester formulations exist: drostanolone propionate, the original pharmaceutical preparation with a short half-life requiring frequent injections (every other day or daily), and drostanolone enanthate, a longer-acting formulation produced by underground labs that permits less frequent dosing (twice weekly). Propionate remains the more widely used and available form.
| Protocol | Dose | Frequency | Route / duration |
|---|---|---|---|
| Cutting / Aesthetic Enhancement Standard cutting dose alongside a testosterone base. Visual effects are most pronounced below 12-15% body fat. Higher doses do not proportionally increase aesthetic benefit and worsen hair loss risk. Run for 8-12 weeks with propionate or 10-14 weeks with enanthate. | 300-400 mg/week | Every other day (propionate) or 2x per week (enanthate) | Intramuscular |
| Contest Preparation Higher end dosing used in the final 6-8 weeks before competition for maximum hardening and drying effects. Often stacked with trenbolone, testosterone propionate, and/or Winstrol. Body fat must be sufficiently low for the full effect to be visible. | 400-500 mg/week | Every other day or daily (propionate) | Intramuscular |
| AI Replacement / Estrogen Management Lower dose used primarily for its anti-estrogenic properties when running moderate-dose testosterone. Can reduce or eliminate the need for anastrozole or other AIs, sparing lipids and joint health. Not a complete AI replacement at high testosterone doses. | 200-300 mg/week | Every other day (propionate) or 2x per week (enanthate) | Intramuscular |
Preparation
You will need
- Pre-filled drostanolone vial (typically 100 mg/mL propionate or 200 mg/mL enanthate in carrier oil)
- Syringes (1 mL or 3 mL)
- Drawing needle (18-21 gauge)
- Injection needle (22-25 gauge for IM)
- Alcohol swabs
- Sharps container
Steps
- Wash hands thoroughly and prepare a clean work surface
- Wipe vial stopper with alcohol swab and allow to dry
- Draw air into syringe equal to the volume of drostanolone to be withdrawn
- Insert drawing needle through vial stopper and inject air to equalize pressure
- Invert vial and withdraw the prescribed dose, tapping to remove air bubbles
- Switch to injection needle (do not inject with drawing needle)
- Clean injection site with alcohol swab in circular motion outward
- Insert needle at 90-degree angle into ventrogluteal, vastus lateralis, or deltoid muscle
- Aspirate briefly (optional per current guidelines), then inject slowly over 10-30 seconds
- Withdraw needle, apply gentle pressure with gauze, dispose of needle in sharps container
Work out the water volume and syringe units in the reconstitution calculator →
Interactions
Pairwise interactions with other compounds you might be cycling — the same data behind the cycle builder's safety check.
Finasteride
AvoidFinasteride inhibits 5-alpha reductase, which converts testosterone to DHT. Since Masteron is already a DHT derivative, finasteride does not reduce its androgenic potency in any tissue. Furthermore, using finasteride while on Masteron is counterproductive: it will not protect against Masteron-induced hair loss (the primary reason for taking finasteride) and may worsen the overall androgenic side effect profile by altering the androgen balance. Individuals concerned about hair loss should avoid Masteron entirely rather than attempting to mitigate it with finasteride.
Testosterone
SynergisticTestosterone is the standard base compound run alongside Masteron. Masteron complements testosterone by providing anti-estrogenic activity that can reduce or eliminate the need for a dedicated AI, while testosterone provides the anabolic foundation and maintains normal physiological function. A common ratio is equal doses or slightly higher testosterone. Masteron enhances the aesthetic quality of a testosterone cycle by reducing water retention and promoting a harder appearance.
Anastrozole
CompatibleMasteron's inherent anti-estrogenic properties often reduce or eliminate the need for anastrozole when running moderate testosterone doses. If both are used, estradiol should be monitored carefully to avoid over-suppression, which can impair joint comfort, lipid health, and bone mineral density. Many users find that adding Masteron to a testosterone cycle allows them to drop their AI entirely or reduce the dose significantly.
Trenbolone
SynergisticA classic pre-contest stack. Both compounds are non-aromatizing and promote a hard, dry, vascular physique. Masteron's anti-estrogenic properties complement trenbolone's potent anabolic and fat-partitioning effects. This combination is commonly used in the final weeks of contest preparation for maximum conditioning. Requires a testosterone base.
Growth Hormone
SynergisticGrowth hormone enhances fat mobilization and promotes a leaner body composition, amplifying the visual effects that Masteron provides. GH-driven reductions in subcutaneous fat make Masteron's hardening and drying effects more visible. The combination is frequently used during contest preparation and advanced cutting protocols.
Timeline
Typical week-by-week effects reported in clinical and observational data.
- Week 1-2
With propionate ester, blood levels stabilize quickly and some users notice a mild mood and confidence boost from the androgenic activity within the first week. No significant visual changes yet. Enanthate users will still be building toward stable blood levels during this period.
- Week 3-4
Anti-estrogenic effects become apparent: reduced water retention, less bloating, and a visibly tighter midsection if body fat is reasonably low. Users on aromatizing compounds may notice improved estrogen management. Early signs of muscle hardness and improved vascularity begin to appear in lean individuals.
- Week 5-8
Peak aesthetic effects for propionate users. Pronounced muscle hardness, dryness, and vascularity at low body fat. The 'granite' or 'grainy' look becomes evident, particularly in the shoulders, chest, and arms. Strength may increase modestly. Hair loss in predisposed individuals typically becomes noticeable during this period.
- Week 8-12
Full steady-state effects for enanthate users. Continued drying and hardening effects. Individuals running Masteron through the final weeks of a contest prep will see the most dramatic visual impact during this phase. Lipid values (especially HDL suppression) should be monitored as duration increases.
Safety
Reported adverse effects, contraindications, and what to monitor on cycle.
Common side effects
- Hair loss and accelerated male pattern baldness (significant risk as a DHT derivative - the most commonly reported side effect)
- Acne and increased skin oiliness, particularly on the back and shoulders
- Suppression of natural testosterone production (requires PCT or ongoing TRT)
- Injection site pain or discomfort (more common with propionate ester)
- Mild aggression or irritability from elevated androgenic activity
- HDL cholesterol suppression and adverse lipid profile changes
Rare side effects
- Prostate enlargement or urinary symptoms in predisposed individuals
- Virilization in women (deepening voice, hirsutism, clitoral enlargement) even at low doses
- Insomnia or restlessness at higher doses
- Left ventricular hypertrophy with prolonged supraphysiological use
- Elevated hematocrit requiring monitoring at higher doses or prolonged use
- Mood changes including depressive symptoms during discontinuation
Stop signs — stop and seek advice
- Severe chest pain, tightness, or pressure
- Sudden shortness of breath or difficulty breathing
- Significant scalp hair loss progressing rapidly beyond baseline shedding
- Swelling, warmth, or pain in one leg (potential deep vein thrombosis)
- Severe or persistent headaches with visual disturbances
- Signs of stroke: sudden numbness, confusion, trouble speaking, loss of coordination
- Persistent urinary difficulty or pain (prostate-related)
Contraindications
- Prostate cancer (active or history of hormone-sensitive prostate cancer)
- Breast cancer in males
- Pregnancy or potential for pregnancy (causes virilization of female fetus)
- Known hypersensitivity to drostanolone or any formulation components
- Severe hepatic impairment
- Pre-existing significant hair loss where further androgenic exposure is unacceptable
- Polycythemia (hematocrit above 54% at baseline)
- Uncontrolled cardiovascular disease or severe dyslipidemia
Monitoring
- Total and free testosterone: baseline and every 6-8 weeks during use
- Estradiol (sensitive assay): important to ensure adequate estrogen levels are maintained, as Masteron's anti-estrogenic effect combined with any AI use can crash estradiol
- Complete blood count with hematocrit: baseline, 6-8 weeks, then every 3 months
- Comprehensive metabolic panel and lipid panel: baseline and every 8-12 weeks (pay particular attention to HDL suppression)
- Liver function tests: baseline and periodic monitoring
- PSA (prostate-specific antigen): baseline and every 6 months for men over 40
- Blood pressure: regular monitoring throughout use
- Hair loss assessment: document baseline hair density if hair preservation is a concern
Quality checks
What a legitimate product looks like, what should give pause, and what should make you stop.
Good signs
- Clear, pale yellow to yellow oil with no visible particles or cloudiness
- Proper labeling with concentration (typically 100 mg/mL propionate or 200 mg/mL enanthate), ester type, and expiration date
- Intact rubber stopper with no signs of prior puncture
- Oil draws smoothly with appropriate viscosity
- Product sourced from reputable supplier with third-party testing (note: no pharmaceutical-grade Masteron currently in production)
Warning signs
- Concentration claims above 150 mg/mL for propionate or 250 mg/mL for enanthate (higher concentrations often cause post-injection pain)
- Vial label with spelling errors, misaligned printing, or unprofessional appearance
- Oil appears slightly darker than expected but is otherwise clear
- No third-party analytical testing documentation available
Stop signs — don't use
- Cloudy, discolored, or particulate-containing solution (contamination risk)
- Crashed product (crystallized steroid visible in vial)
- Broken or missing tamper-evident seal on vial
- No labeling, incorrect labeling, or missing expiration date
- Pain, redness, or swelling at injection site lasting more than 72 hours (potential infection or abscess)
- Product sourced without any testing or third-party verification
Recent research
Newer papers and trial readouts on file for this compound, with source and date.
March 2020 · International Journal of Environmental Research and Public Health
A Systematic Review of the Effects of Different Types of Anabolic Androgenic Steroids on Lipid Metabolism
Systematic review documenting that DHT-derived steroids including drostanolone produce significant HDL cholesterol suppression, reinforcing the importance of lipid monitoring during Masteron use and keeping cycle lengths moderate.
September 2006 · Journal of Chromatography B
Detection of Drostanolone and Its Metabolites in Human Urine by Gas Chromatography-Mass Spectrometry
Study characterizing the urinary metabolites of drostanolone for anti-doping detection. Identified key metabolites including 2-alpha-methyl-5-alpha-androstan-3-alpha-ol-17-one and established detection windows for propionate and enanthate esters.
January 2017 · Circulation: Heart Failure
Cardiovascular Effects of Anabolic Steroids: Cross-Sectional Study of Male Strength Athletes
Cross-sectional study of 140 strength athletes finding that long-term anabolic steroid use was associated with reduced left ventricular systolic function and increased coronary artery plaque volume, applicable to all anabolic steroids including DHT derivatives like Masteron.
References
Primary literature and clinical-trial data informing this entry.
Drostanolone Propionate (Masteril): A Short Review of a Discontinued Breast Cancer Drug
Raynaud, J.P. · Journal of Steroid Biochemistry and Molecular Biology · 1988
Review of drostanolone propionate's clinical use in inoperable breast cancer, documenting its anti-estrogenic properties and mechanisms. Demonstrated objective tumor regression in a subset of postmenopausal patients with hormone-receptor-positive disease, supporting its classification as a hormonal antineoplastic agent.
Androgens and the Treatment of Breast Cancer
Goldenberg, I.S. · Cancer · 1964
Early clinical report on the use of androgenic steroids including drostanolone in breast cancer treatment. Documented objective response rates and the dual mechanism of direct anti-tumor effects and anti-estrogenic activity that formed the basis for FDA approval.
Anabolic-Androgenic Steroid Use and Body Image in Men: A Growing Concern for Clinicians
Kanayama, G., Hudson, J.I., Pope, H.G. · Psychotherapy and Psychosomatics · 2012
Comprehensive review covering the pharmacology and health effects of anabolic-androgenic steroids including DHT derivatives like drostanolone. Documented dose-dependent cardiovascular, hepatic, and endocrine adverse effects associated with long-term use.
Adverse Effects of Anabolic Androgenic Steroids on Cardiovascular System
Achar, S., Rostamian, A., Narayan, S.M. · Southern Medical Journal · 2010
Review of cardiovascular toxicity associated with anabolic steroids, documenting HDL cholesterol suppression, left ventricular hypertrophy, and thrombotic risk. Emphasized the importance of cardiovascular monitoring in individuals using DHT-derived compounds like Masteron.
Comparison of the Pharmacokinetics of Testosterone Propionate and Testosterone Enanthate
Nieschlag, E., Behre, H.M. · Testosterone: Action, Deficiency, Substitution (Cambridge University Press) · 2004
Pharmacokinetic analysis of propionate versus enanthate ester formulations applicable to understanding drostanolone ester behavior. Propionate demonstrates a half-life of 1-3 days with rapid peak levels, while enanthate extends the half-life to 7-10 days, directly informing injection frequency protocols for both Masteron esters.
Last updated . How this page was sourced is described in the methodology.