Evidence memo / Anabolic androgens & PEDs

Drostanolone (Masteron)

Also: masteron · drostanolone propionate · dromostanolone

An androgen once used to treat breast cancer, long abandoned for that purpose, now used almost entirely cosmetically in the final weeks before a contest on the basis of appearance rather than any measured outcome.

Claim-specific / contestedContext-dependentSafety / regulatory watch

The verdict

Our read at a glance.

Whether a discontinued oncology androgen has any evidence base for the cosmetic effect it is now used for.

The signal
Its historical clinical use was as an androgen therapy in advanced breast cancer in women, a role superseded decades ago by tamoxifen and aromatase inhibitors with far better efficacy and tolerability. There is no modern efficacy literature and no controlled trial in the population using it now. The contemporary indexed record is dominated by analytical and anti-doping chemistry: metabolite characterisation, detection methods and the biotransformation studies that underpin them. The cosmetic effect it is used for - a visual change in muscle definition at low body fat - has never been measured in a study.
The unknown
Whether the effect is pharmacological at all, or an artefact of the extreme dieting, dehydration and low body fat that accompany its use. Nothing in the literature separates those.
Our read
A drug that lost its medical job to better medicines and found a second career as a cosmetic. The effect people describe may well be real, but it has never been measured, and it is being taken at the precise moment - deep contest dieting - when the body has the least margin for a non-aromatising androgen.

The mechanism

How it works.

Drostanolone is a dihydrotestosterone derivative with a 2-alpha methyl group, added to slow its inactivation by the enzyme 3-alpha-hydroxysteroid dehydrogenase so that more of it survives to act at the androgen receptor. Because it is already 5-alpha reduced it cannot be converted by aromatase, so it produces no oestradiol at all. It also binds aromatase itself with some affinity without being converted, which gives it weak anti-oestrogenic activity and is the basis of the claim that it dries out the physique. That is the mechanism, and it also explains the cost: the visual effect depends on removing oestrogen-associated subcutaneous water, and oestradiol in men is doing useful work on lipids, bone density and endothelial function while it is being removed.

Safety & regulatory boundary

The consequential part.

No current approved human product; a Schedule III controlled substance in the United States. It is a dihydrotestosterone derivative and does not aromatise, so it produces no oestradiol and offers none of oestrogen's protective effects on lipids, bone and endothelium while suppressing the user's own testosterone. Strongly androgenic relative to its anabolic effect, so scalp hair loss, acne and, in women, virilisation are the predictable liabilities. Prohibited in sport.

What's next

What we're watching.

Nothing in development. Continued anti-doping detection work is the only active literature.

Context

Why this is discussed.

It has a strong reputation for hardness and dryness in the final weeks of contest preparation, and for mild anti-oestrogenic activity that removes the need for a separate drug.

The evidence base

12 cited references.

Indexed literature (PubMed)12

Exploring the Polymorphism of Drostanolone Propionate

Borodi G et al. · Molecules · 2020

Keep reading

Related published memos.