Proviron side effects

Proviron is a pharmaceutical derivative of the steroid hormone testosterone. Doctors prescribe this drug to treat hypogonadism, and athletes and bodybuilders have used it illicitly. Patients with certain pre-existing conditions should avoid taking Proviron, as its use can lead to a number of detrimental side effects.


Proviron is Bayer's brand name for the steroid hormone mesterolone, a testosterone derivative that strongly resembles the chemical structure of Dihydrotestosterone (DHT). Testosterone is a naturally occurring hormone produced by the testes, ovaries and adrenal glands. DHT results from a natural conversion of testosterone caused by the 5-alpha reductase enzyme.

Like testosterone, Proviron exhibits strong androgenic (masculinising) effects, and according to Muscle Sports Mag's Leigh Penmen, Proviron also exerts mild anabolic (tissue building) effects as well.


The Bayer website reports that doctors can prescribe Proviron to treat hypogonadism, a condition in which a man's body no longer produces enough natural testosterone. Hypogonadism can cause a decrease in skeletal muscle mass and concurrent increase in fatty tissue deposits, a decrease in bone density, lessened libido and erectile dysfunction, depression, fatigue and a general poor state of mental health and well-being. By replacing natural testosterone, Proviron can alleviate or reverse these symptoms.

Effects of Illicit Use

Penman points out that bodybuilders and strength athletes have used Proviron illicitly to mediate the effects of steroid use, particularly the side effects of excess testosterone. Proviron binds strongly to the aromatase enzyme, a naturally occurring chemical, which converts excess testosterone to oestrogen. By using 25 to 100 mg a day, Penman states that bodybuilders can reduce the risk of gynaecomastia, which is the development of male breast tissue caused by the conversion of testosterone into oestrogen. In addition, because Proviron chemically resembles DHT, athletes gain many of the DHT's benefits, including enhanced muscle hardness and increased strength. Bayer's information on Proviron concurs with Penman's assessment, by noting that Proviron use may lead to strength improvements.


The British pharmaceutical website Net Doctor reports that Proviron should not be used by patients with pre-existing liver tumours. As Proviron can enlarge the prostate, elderly men or men with pre-existing prostate cancer should also avoid using Proviron.

Bayer additionally reports that patients with hypercalcemia (high blood levels of calcium) should not take Proviron, and that before taking Proviron, patients with high blood pressure, diabetes, kidney disease, epilepsy or heart disease should consult with a physician to discuss risks and complications to these conditions that Proviron might cause.

Children, women who are pregnant or women who could become pregnant should avoid using this drug. states that androgens given to pregnant women have caused female foetuses to develop masculine feature, and that externally administered androgens may stunt the growth of children.


Because Proviron resembles DHT and is derived from testosterone, it will exhibit strong masculinising effects that may include a deepened voice, excess growth of facial and body hair, acne, oily skin and male pattern baldness. reports that high dosages of androgens in men can interfere with sperm production.

Women are more prone to experience these masculinising effects, and women taking Proviron might also experience changes in their physique, such as greater muscle mass and a redistribution of adipose tissue (including decreased breast size), that make their bodies more resemble adolescent boys. In addition, women taking any androgens might suffer from an altered libido, disruption of the menstrual cycle or an enlarged clitoris.


Net Doctor reports that in rare cases, androgens similar to Proviron have caused patients to develop liver tumours that may be life-threatening. The most common side effect of Proviron is persistent and frequent erections.