Some bodybuilders and athletes use trenbolone esters for their muscle-building and otherwise performance-enhancing effects.  Such use is illegal in the United States and many other countries. The DEA classifies trenbolone and its esters as Schedule III controlled substances under the Controlled Substances Act .  Trenbolone is classified as a Schedule 4 drug in Canada  and a class C drug with no penalty for personal use or possession in the United Kingdom .  Use or possession of steroids without a prescription is a crime in Australia .  The infamous "duchess" cocktail administered to Russian athletes at the Sochi Winter Olympics consisted of oxandrolone , a metenolone ester, and a trenbolone ester. 
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.
A commonly used protocol for determining the androgenic:anabolic ratio, dating back to the 1950s, uses the relative weights of ventral prostate (VP) and levator ani muscle (LA) of male rats. The VP weight is an indicator of the androgenic effect, while the LA weight is an indicator of the anabolic effect. Two or more batches of rats are castrated and given no treatment and respectively some AAS of interest. The LA/VP ratio for an AAS is calculated as the ratio of LA/VP weight gains produced by the treatment with that compound using castrated but untreated rats as baseline: (LAc,t–LAc)/(VPc,t–VPc). The LA/VP weight gain ratio from rat experiments is not unitary for testosterone (typically –), but it's normalized for presentation purposes, and used as basis of comparison for other AAS, which have their androgenic:anabolic ratios scaled accordingly (as shown in the table above). In the early 2000s this procedure was standardized and generalized throughout OECD in what is now known as the Hershberger assay.