How long until testicular atrophy is irreversible?

Does anyone know how long (if it happens at all) are testicules irreversibly atrophied from HRT? Basically I'm scared that if I stop HRT they'll just go back to working the way they always have and I'm hoping that they won't.

I've been on HRT mono therapy for a year now and my testosterone has been nearly totally suppressed for the whole time, so I wonder if the girls are done for essentially...