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.
When activated macrophages start to secrete IL-1, which synergistically with CRH increases ACTH,  T-cells also secrete glucosteroid response modifying factor (GRMF), as well as IL-1; both increase the amount of cortisol required to inhibit almost all the immune cells.  Immune cells then assume their own regulation, but at a higher cortisol setpoint. The increase in cortisol in diarrheic calves is minimal over healthy calves, however, and falls over time.  The cells do not lose all their fight-or-flight override because of interleukin-1's synergism with CRH. Cortisol even has a negative feedback effect on interleukin-1  —especially useful to treat diseases that force the hypothalamus to secrete too much CRH, such as those caused by endotoxic bacteria. The suppressor immune cells are not affected by GRMF,  so the immune cells' effective setpoint may be even higher than the setpoint for physiological processes. GRMF affects primarily the liver (rather than the kidneys) for some physiological processes. 
It could be argued that aromatization is a non-issue, as an . could always be employed to counter estrogen conversion. This is true, but I believe there is a simpler way to go about it. In my opinion, the ideal pre-contest MPD cycle should consist of a low dose of testosterone propionate (150-200 mg/week), as at least some estrogen is needed to maintain a healthy looking skin tone. This should be combined with 2-3 other anabolics; preferably 1-2 oral anabolics and 1-2 injectables anabolics. Some good examples of orals include: Anavar, Epistane, and Turinabol. As for injectables, most people usually find the following drugs to be compatible: Primo, Boldenone, and Dihydroboldenone (1-testosterone).