Certainly, the earlier you start, the better your results. I have regrets that I didn't start when I was 14 the year I left my parents of course, I didn't even understand that a transition was medically possible and the internet wasn't quite the resource it is today (I would have been 14 in 2000). I tried to get things together to start at 24, but it didn't happen till I was 28! I am 29 now (look at the date it is my B-day 😛 )...... That being said, what can I do about it? I mean I don't have a time machine, it probably wouldn't be a wise investment of my time to try and figure out how to build one (because I am sure people smarter than me have tried), so the question is then what is a smart investment of time.
The way I see it, the smartest investment of time, is to be the best you that you can possibly be. I know Testosterone did damage, to me, but nothing stops me now, from taking any and every step to getting rid of that damage. I can't have stopped it from occurring, but that is no reason to give up and settle. I am amazing, and I would never settle for being anything less than what I am.
So yes, I might need a bit of surgical work to be how I want to be, it might take me longer to get there, but, no one, not even the teenage me, can stop me.