Lastly, all anabolic steroids are known to be suppressive to the HPTA (Hypothalamic Pituitary Testicular Axis), which results in a suppression and/or total shutdown of endogenous natural Testosterone production. This is one of the reasons why cycles must be kept as short as possible, as the longer a cycle is run the more difficult it is for one to restore their endogenous production of hormones. Dbol is very well known for its strong suppressive nature. Studies have been conducted on Dianabol’s suppressive nature in particular, and they have demonstrated that doses as low as 15mg per day for 8 weeks caused mean plasma Testosterone levels to decline by 69%  . It is very important that following any cycle, the user engages in a Post Cycle Therapy (PCT) program, which includes the use of Testosterone-stimulating compounds (such as Nolvadex ) for a 4-6 week period in order to ensure full restoration of the body’s endogenous production of Testosterone and related hormones. Without a proper PCT program, the user risks damaging and/or shutting down his HPTA for the rest of his life.