Mesterolone is an androgen and anabolic steroid (AAS) medication available in tablet form, primarily used to treat conditions in men caused by a deficiency of natural male sex hormones (androgens), such as male hypogonadism and certain types of male infertility. It is a prescription drug marketed under brand names like Provironum. 

Key Information

• Medical Uses: Mesterolone is used to restore normal testosterone levels in men, which helps improve symptoms like fatigue, low libido, and decreased muscle strength. It may also support sperm production and maturation in men with fertility issues related to low androgen levels.

• Mechanism: The active ingredient, mesterolone, is a synthetic steroid hormone that supplements the body's natural male hormone (testosterone). It has strong androgenic effects but weak anabolic effects. A key characteristic is that it does not convert to estrogen, which avoids estrogenic side effects like gynecomastia or fluid retention.

• Administration: It is an oral medication, typically available as 25 mg tablets. The tablets can be taken with or without food, usually several times a day as prescribed by a doctor.

• Availability: Mesterolone is widely available in many countries, including the UK, Australia, and South Africa, but it has never been marketed in the United States, Canada, or New Zealand.

• Non-Medical Use: It is sometimes used for physique- and performance-enhancing purposes by bodybuilders and athletes, although this use is not generally recommended due to its weak anabolic effects and potential side effects. Non-medical use is generally illicit in many countries as it is a controlled substance.