===================== GO TO OUR ONLINE STORE: https://t.co/VBWHH4dD05 ===================== Bayer Proviron is used as an aromatase inhibitor. The drug helps increase the level of natural testosterone production, which leads to fewer negative effects caused by potent anabolic steroids. Bayer Proviron is a brand name for Mesterolone. Proviron was developed in 1934 by Shering which makes it among the oldest pharmaceutical steroids for therapeutic use. You may have never heard of it as it was never marketed in the USA, but is available around the world in places such as the UK, New Zealand and Mexico to name a few.