The only way an increase in testosterone would increase the size of your penis is if there was a clinic that discovered the right gene that turned on the growth factors of the penis during birth and puberty and were able to flip the switch on that gene or genes while administering testosterone therapy injections or natural testosterone enhancing supplements, triggering your body to produce more testosterone. They would also need to find the right balance of other hormones that also play a part in developing reproductive organs.
I don’t see the point in taking steroids. Doing it would shrink the testicles anyway because your body would sense the increase of the synthetic testosterone and increase the estrogen receptors in your brain and would trigger your body to stop producing natural testosterone on it’s own which ultimately defeats the purpose.
That’s my opinion on it anyway.