Initially, that is the case, but not necessarily in a dose-dependent manner to extremes. If this were the case, anyone would be able to get huge off a couple megadose cycles. There just comes a time when one becomes so large that the body has trouble maintaining the mass, and to overcome these counterproductive effects, megadoses are one way of potentiating a greater possibility of AAS binding ARs. There is little data on receptor upregulation (ARs), but there is enough to convince me. There IS also evidence of receptor downregulation over time in response to high levels of AAS (testosterone). The latter studies were in cell culture, but those that argue against the theory of receptor downregulation seem to neglect to mention those studies or downplay their significance. Rarely have I seen anyone who argues against receptor downregulation pose a reasonable possibility as to why growth does seem to plateau. It's not cortisol and catabolism while on AAS...we know that.....it's not SHBGs or serum albumin titrating the AAS, because we know that although these levels go up, they don't continue to elevate so as to normalize sex hormone (AAS) and estrogen levels to that of a nonAAS user. What is it then?? Why do gains cease as a cycle progresses....only to be revived again after a period of off time?