Quote Originally Posted by MuscleScience View Post
It does, but not by receptor down regulation. There is a concept called negative feedback inhibition (aka: negative feedback loop) in regards to hormone regulation in the body. For example when testosterone is high in the body. The pituitary gland (anterior pituitary) senses this and decreases the secretion of Luteinizing hormone, which acts on the Leydig cell of the testis to produce testosterone. The process works in reverse when testosterone is low.

Keep in mind this is a very simplistic example and there are of course other process the affect circulating testosterone. In general this is a good way to describe how the body self regulates itself.
But this process will happen whether your injecting a small or large amount of supplemental test. You can run your test at 100mg a week or 1000mg a week and the process of this negative feedback loop will take place. You can also run a cycle for 2 weeks or 12 weeks and the process will still be the same. As you said prior, if you are introducing supplemental test. your leydig cells will stop producing testosterone no matter the cycle length or dose of testosterone. Please correct me if I am wrong. That's why we run PCT so as to stimulate those leydig cells. I know this is simplified but isn't that the just of it.