The Mesterolone hormone is not estrogenic. It does not aromatize and it carries no progestin nature. As a result, the side effects of Proviron will not include any related effects such as gynecomastia or excess water retention. Such adverse effects are impossible with this steroid. This will also greatly reduce the risk of high blood pressure as high blood pressure associated with anabolic steroid use is often due to extreme water retention. In fact, Proviron should provide an anti-estrogenic effect by preventing testosterone to estrogen conversion or at least tremendously slow it down.
Proviron has four distinct uses in the world of bodybuilding. The first being the result of its structure. It is 5-alpha reduced and not capable of forming estrogen, yet it nonetheless has a much higher affinity for the aromatase enzyme (which converts testosterone to estrogen) than testosterone does. That means in administering it with testosterone or another aromatizable compound, it prevents estrogen build-up because it binds to the aromatase enzyme very strongly, thereby preventing these steroids from interacting with it and forming estrogen. So Mesterolone use has the extreme benefit of reducing estrogenic side-effects and water retention noted with other steroids, and as such still help to provide mostly lean gains. Its also been suggested that it may actually downgrade the actual estrogen receptor making it doubly effective at reducing circulating estrogen levels.
Testosterone enanthate ( USAN , BAN ) (brand names Delatestryl , Testostroval , Testro LA , Andro LA , Durathate , Everone , Testrin , Andropository ), or testosterone heptanoate , is an androgen and anabolic steroid and a testosterone ester .    Along with testosterone cypionate and testosterone propionate , it is one of the most widely used testosterone esters.  Testosterone enanthate was first introduced in 1952.  Administered via intramuscular injection , it is the most widely used form of testosterone in androgen replacement therapy .