Proviron (mesterolone) is an oral form of DHT-type androgen that was prescribed for low testosterone and male infertility. It is strongly androgenic but only weakly anabolic, gentler on the liver than most orals, and mainly used alongside other compounds rather than on its own.
- Not 17-alpha-alkylated, so liver strain is low compared with other orals.
- Binds strongly to SHBG and does not convert to estrogen.
- Can still lower HDL cholesterol and suppress natural testosterone.
Proviron is an odd compound. It does little for muscle size, yet it remains popular with experienced users. Understanding why requires a quick look at how it works and what it was designed to do.
What mesterolone is
Mesterolone is 1-alpha-methyl-dihydrotestosterone. It was developed by Schering in the 1930s and marketed as Proviron from the 1960s for men with low testosterone and some forms of infertility. Unlike most oral steroids, it is not 17-alpha-alkylated. Instead, the methyl group at carbon 1 slows its breakdown enough to allow oral use, which means much less strain on the liver.
Proviron was sold in many countries, mainly in Europe, but has not been marketed in Canada.
How it works
- Strong androgen, weak anabolic. Like DHT, it is broken down in muscle tissue before it can have much effect there, so muscle growth is limited.
- No estrogen conversion. As a DHT derivative, it cannot be aromatised.
- High SHBG binding. Mesterolone binds strongly to sex hormone-binding globulin (SHBG), the protein that carries testosterone in the blood. In theory this frees up more testosterone from other sources, which is one reason it is used alongside them.
- Less suppression at low doses than most steroids, which is why it was used for infertility, though higher doses do suppress.
Why people add it
Experienced users describe it as improving libido, mood and a “harder” look in lean people, and some use it to offset the low libido associated with low estrogen or nandrolone. There is little research on these uses in healthy people, so these are user reports rather than proven effects.
A common belief is that Proviron acts as an anti-estrogen. Some lab research suggests DHT derivatives can reduce aromatase activity, but the effect in people is not well established. It is not a substitute for proper estrogen management when estradiol is genuinely high.
Side effects
- Androgenic effects: acne, oily skin and hair loss in those prone to male-pattern baldness, since it is closely related to DHT
- Cholesterol: lower HDL, as with other oral androgens
- Prostate: DHT drives prostate growth; men with prostate enlargement or a history of prostate cancer should not use it
- Suppression of natural testosterone at higher doses
- Low estrogen symptoms if used to push estradiol down: joint aches, low libido, low mood
- In women, rapid masculinising effects
Proviron and hair loss
Because mesterolone is a DHT derivative, it can speed up male-pattern hair loss in men who are genetically prone. Finasteride, which blocks the conversion of testosterone to DHT, does not block mesterolone itself, since it is already in DHT form. Anyone concerned about their hairline should consider this before use.
Bloodwork
Useful tests include total testosterone, SHBG, estradiol, a lipid panel, PSA where appropriate, a complete blood count and liver enzymes. Your doctor can order them, or you can pay privately at LifeLabs or Dynacare; see our bloodwork guide.
Where it fits
Proviron is usually described as a supporting compound for experienced users, not a first or standalone one. For a first experience, testosterone alone remains the standard advice; see a first testosterone course. For other orals and their liver profiles, see oral steroids compared.
Products and legal status
We carry Zionova Proviron 20 mg, with batch lab results on the product page. Mesterolone is a Schedule IV controlled substance in Canada and is banned in sport.
Frequently asked questions
Does Proviron build muscle?
Very little. It is strongly androgenic but weakly anabolic because it is broken down in muscle tissue.
Is Proviron liver toxic?
It is much gentler on the liver than most orals because it is not 17-alpha-alkylated, though liver tests are still sensible.
Does Proviron cause hair loss?
It can in men prone to male-pattern baldness, as it is a DHT derivative. Finasteride does not block it.
Photo: Tmeers91, Wikimedia Commons (public domain).
General information, not medical advice. Mesterolone is a Schedule IV controlled substance in Canada.
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