Firstly I want to state that this is a FACT of human physiology. Not what may or may not happen because a piece of literature or two say so.

Now bear with me, because I want to make sure everyone understands this.

I'm sure you're familiar with how people say that fat cells never "disappear", only shrink? Well this is obviously true. The fat cells you gain will only shrink in size but will always be present in your body - Along with all the necessary cellular components of the cell to function (nucleus where the genetic information is held, ect).

Fat cells are obviously specialised cells geared towards storing adipose tissue. And since the genetic information "hardwired" to storing fat will always be retained (as the cell does not disappear, only shrinks), gaining fat will always be EASIER for those who were previously obese, and have a greater number of fat cells still present in their body.

This is a legitimate reason why people are encouraged to lean bulk and not dirty bulk.

Anyway, its almost the SAME thing with a muscle cell (specialised cell). I'd like to make it clear that this is also THE MUSCLE MEMORY PEOPLE KEEP TALKING ABOUT. Muscle memory is a FACT and all you need to do is understand this little mechanism of human physiology to understand that it is.

Above I also said "Almost" the same thing, as we know that you don't "gain" muscle cells under normal conditions (what HGH may or may not do aside) - You're stuck with the amount you were born with.

But the muscle cell, like the fat cell, can shrink in size, but it will never "disappear" and will retain all its cellular components necessary to its function.

Now when you use steroids, there are only a certain amount of AR in the body. Once your body uses up all the AR, it will do something very intelligent - CREATE MORE androgen receptors within the muscle cell.

Therefore, whenever a satellite cell fuses with a muscle cell, it donates an androgen receptor. Steroids increase the rate at which these satellite cells fuse.

Now, because of this, if you ever stop training and lose the size of your muscle cells, you will always retain the cellular components of the muscle cell. That includes the AR and any extra ones that the body has produced along the way. This is muscle memory in the flesh.

And obviously, the bigger the person, the more AR they have.

Now I know what you're thinking and yes, from this theory, we can confidently deduce that the body becomes UPREGULATED from many years of training and steroid use (Isolated or together). Meaning, there is NO SUCH THING AS YOUR FIRST CYCLE IS YOUR BEST - THIS IS A PSYCHOLOGICAL ISSUE. Your body will only become BETTER are processing steroids, whether they be your natural production or exogenous.

However, even though the bodies growth is not regulated through the androgen receptor, it IS THROUGH OTHER MECHANISMS (Myostatin for one, being a huge one that everyone should know about). This is why we can't keep growing to 500lbs, 5% or 300lbs, 10% from using everything under the sun for a year. I'm just saying that the AR does upregulate, not downregulate, and is not the source of growth prevention but promotion instead.

This is why Bodybuilding will always, no matter what, take dedication, patience and time.

So that's why a pro, or someone who is OR WAS in the past bigger than another person, will always have more AR. Effectively, they have the ability to utilise more steroids and benefit more off smaller dosages VS someone smaller.