There are no actual medical studies on any of this, so its all case report basis from guys like us on boards like this. The strange thing is that women can be estrogen-progesterone mix for birth control for decades, come off the pill, then have a baby the very next month. It may be dosage related, as the pill is very small amounts of hormone, or it may be that that the hypothalamus-pituitary-gonadal axis in women is fundamentally different, but men definitely show more permanent shut down after even moderate AAS use, regardless of age. My educated guess as a medical person is that regardless of your age, AAS usage for say 2-3 years could seriously compromise your natural ability to produce testosterone for the rest of your life. What if you only do a couple cycles? Maybe then you can fully recover, but very few of us only do a couple of cycles. Again, my guess is that extended AAS use irreversibly impacts your HPTA for the rest of your life, possibly by killing the responding cells in either your testis or even in the hypothalamus (feedback neurons) or pituitary. Just be prepared for TRT the rest of your life, and poor sexual function. Price you pay if you want to get big.