OP was mostly concerned about growth plate fusing, and it so happens that Femera - letrozole - also stops plate fusing in adolescents in higher doses.
And you can permanently shut down at 17 as well as 24 if you're prone, so unless you become father in meantime you'll need HCG - human chorionic gonadotropin - - human chorionic gonadotropin - shots and TRT anyways. And most long term users end up on TRT anyway, thats how it goes, sorry. Kids shouldn't use steroids, but if they think they made conscious decision probably cutting their source is the only thing that would stop them.
Anyway thats what you get for shunning the topic, maybe kid above would be using 20mg of Winstrol - stanozolol instead of cow medicine if somebody would admit that its way fucking safer for him.