Testosterone or Masteron: What Is the Difference

Masteron is the trade name of drostanolone, a derivative of dihydrotestosterone. Unlike testosterone, it is not converted into estrogens, and it is precisely this property that shapes both its reputation and its specific risks. The editorial team explains how these two substances differ at the level of the molecule, metabolism, and effect on the body.

Two different families of androgens

Synthetic anabolic-androgenic steroids are usually divided into several groups by their parent molecule: derivatives of testosterone, derivatives of 19-nortestosterone (nandrolone), and derivatives of dihydrotestosterone (DHT). Testosterone is the progenitor of the first group, while drostanolone belongs to the third.

This classification is not a formality. The parent molecule determines whether a substance can be converted into estrogens, whether it will be a substrate for 5α-reductase, and how enzymes in various tissues will inactivate it. It is precisely these properties that determine the practical differences between the drugs.

In the human body testosterone acts as a prohormone: part of it is converted into estradiol, part into DHT, and each of these metabolites has its own effects. Drostanolone, by contrast, is already a "reduced" molecule, so these conversions are impossible for it.

Thus, in comparing testosterone and masteron, we are comparing a universal hormone with a broad spectrum of action against a narrowly targeted DHT derivative in which part of the metabolic pathways is simply "switched off."

The structure of the molecule and what follows from it

The chemical name of drostanolone is 2α-methyl-5α-androstan-17β-ol-3-one. From DHT it differs only by a methyl group at the second position of ring A. In pharmaceutical forms it was used as the propionate ester; on the illegal market the enanthate is also encountered.

DHT is a potent androgen, but in skeletal muscle it is rapidly inactivated by the enzyme 3α-hydroxysteroid dehydrogenase. According to classical understanding, the methyl group at position 2α makes drostanolone more resistant to such breakdown, which explains its anabolic activity being higher than that of DHT itself.

Testosterone has a double bond between the fourth and fifth carbon atoms. It is precisely this bond that allows enzymes to convert it into estradiol (aromatization) and into DHT (5α-reduction). Drostanolone lacks this bond, so both conversions are impossible.

As a result, testosterone acts "through three channels" — itself, through DHT, and through estradiol — whereas drostanolone acts only through the androgen receptor. This explains why their profiles of action and side effects differ noticeably.

Estrogens: presence and absence

The absence of aromatization is masteron's key difference. During testosterone use in supraphysiological amounts, the estradiol level also rises, which can cause gynecomastia and fluid retention. Drostanolone by itself does not produce this effect.

However, estrogen is needed in men. It participates in maintaining bone mineral density, regulating libido and lipid metabolism, and, probably, protecting the vessels. An androgen that does not aromatize, when used on its own against a background of suppression of one's own testosterone, can lead to an estrogen deficiency.

Clinical studies in men in whom both testosterone and estradiol were artificially suppressed (in particular, the work of Finkelstein and colleagues, 2013) showed that it is precisely estrogen that is responsible for part of the changes in adipose tissue and libido. This illustrates that the "absence of estrogens" is not an unambiguously positive property.

A second aspect — drostanolone, as a DHT derivative, was studied in early work as an agent with anti-estrogenic action in breast tissue. This property was used in oncology, but it should not be confused with safety for men.

History of medical use

Testosterone has been used in medicine since the 1930s and today is the foundation of replacement therapy for hypogonadism. Its efficacy and safety within physiological levels have been studied in large randomized trials, in particular the TRAVERSE program on cardiovascular safety.

Drostanolone propionate appeared in the 1950s–1960s and was used mainly as an agent for palliative therapy of advanced breast cancer in postmenopausal women. Later it was displaced by more effective and better-tolerated drugs — antiestrogens and aromatase inhibitors.

As a result, in most countries pharmaceutical drostanolone products have gone out of circulation. There are practically no modern clinical studies with it, and new human safety data are not accumulating.

This is a typical situation for many "classic" anabolic steroids: their pharmacology is known from mid-twentieth-century studies, while all modern information about their use in sport comes from informal sources, doping analysis, and descriptions of complications.

Side effects: shared and distinct

Shared for both substances are effects associated with activation of the androgen receptor at supraphysiological levels. Among them are suppression of the hypothalamic-pituitary-gonadal axis, reduced HDL, myocardial changes, psycho-emotional effects, and virilization in women.

The differences concern mainly estrogenic and androgenic effects in the skin and hair.

• Gynecomastia and fluid retention are more characteristic of testosterone due to the formation of estradiol.
• For drostanolone, as a DHT derivative, androgenic effects are considered typical: acne, oily skin, acceleration of androgenic alopecia in people with a genetic predisposition.
• 5α-reductase inhibitors (for example, finasteride) can reduce the DHT-dependent effects of testosterone, but they do not affect drostanolone, since it is already a 5α-reduced molecule.
• Estrogen deficiency against a background of suppression of one's own testosterone is a specific risk of non-aromatizing androgens.

As for the liver: the injectable esters of both substances lack 17α-alkylation, so their hepatotoxicity is significantly lower than that of oral methylated steroids. However, this does not reduce the effect on lipids and the heart.

Finally, masteron, unlike testosterone, is almost always obtained from illegal sources. Thus, on top of the pharmacological risks come the risks of composition discrepancies, impurities, and non-sterility.

Editorial conclusions

Testosterone is a universal hormone whose action is realized both directly and through DHT and through estradiol. Masteron (drostanolone) is a DHT derivative that acts only through the androgen receptor and does not aromatize.

The absence of estrogenic effects does not make masteron safer: it changes the risk profile — toward androgenic effects on skin and hair and a possible estrogen deficiency.

The key systemic risks — suppression of the hormonal axis, dyslipidemia, effects on the heart — are shared by both substances.

We also recommend reviewing our materials on the role of estradiol in the male body, on androgenic alopecia and DHT, and on control of the lipid profile.

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