The body has a very complex system of checks and balances when it comes to stasis. Your "normal" levels are constantly being achieved, broken, and reachieved. When taking a supplement that affect testosterone levels, particularly when tricking the body into thinking that it is coming from an outside source, the body compensates for it by shutting down natural testosterone production. I think that in this system, if you were to stop the cycle of whatever, the body is still producing the same amount as on-cycle for a while until everything comes back to stasis. Estrogen rebound, or an upshoot in conversion, may occur after the cycle is finished as a way for the body to reattain that balance.