Can you cite your sources for permanently impacting brain development? Because I've never seen any.
Also I'd believe if that were factually true, doctors wouldn't/couldn't prescribe testosterone to adolescents undergoing sexual reassignment at the risk of brain development/maturity. It's odd how people will be so harsh judging males for using exogenous testosterone but this goes really untouched. Males in adolescence and early 20s can still have hypergonadism and need treatment. But whatever method that may be, would be based on a per patient basis.
The truth is, nobody has done long term studies enough to prove exogenous testosterone supplementation is the cause or can cause any health risks you already aren't at risk of. Saying otherwise is a very old method of thinking from back when the US made steroids a controlled substance. Unsubstantiated claims of death, disease, etc, an the "people" who came forth claiming their ailments on steroids left out all their immense recreational drug usage, pre-existing conditions, etc. Had to have good reason to ban it. Just like 2006, find some scape goats. The legality of restricting those studies from happening now though, with it being relatively easy to find long term patients on TRT, will hopefully change.
Mind you (anyone) I said exogenous testosterone. I did not say, tren, bold, deca, etc. Just plain old test. Granted most steroids were developed for their respective medical purposes, muscle wasting, yadda yadda. Tren/EQ and some others were not designed for humans.
By no means am I saying this is a route for everyone, not saying they're harmless and okay, you have to weigh the pros and cons.
Not trying to argue, simply a fruitful discussion.
Regards.