Mesterolone

• "Proviron" is the brand name mesterolone, which is a molecule that is structurally very similar to the hormone testosterone. However, while testosterone is eventually broken down by enzymes into estrogen, these same enzymes cannot metabolize mesterolone. Therefore, some body builders take a mesterolone in hopes of getting the muscle-building effects of testosterone without suffering the unwanted side effects of increased estrogen levels afterward.
  
  

From Mesterlone To Androsterone

• Enzymes in muscle tissue convert mesterolone's carbonyl (C=O) to a hydroxide (-OH) and its original hydroxide group to a carbonyl, resulting in a compound called "1α-methyl-androsterone." This metabolite waste is taken from the muscles to the liver, via the veins.
  
  

Glucuronidation In The Liver

• Once in the liver, 1α-methyl-androsterone is recognized by cells as a toxin. In response, special enzymes bind molecules of glucuronic acid to it. Because glucuronic acid is very soluble in water, surrounding the 1α-methyl-androsterone with it makes the latter more soluble as well. This process is known as "glucuronidation" and is commonly used by the liver to treat toxin molecules.
  
  The glucuronidated molecule dissolves in the blood, allowing it to pass through the kidneys and into the bladder. Finally, the metabolite is expelled from the body through urination.