Depending on the cycle, it may lower your sperm count making at more difficult. But infertile...no. Lots of good bros on this board are now fathers while they were on.
A good HRT service will make sure you never really shut-down -- but the HRT will supress your natural production at almost any dose. That's why even on low-dose HRT, you'll either do medium cycles (i.e. 10 on, 4 off) or they'll just string you out between shots (i.e. 2-3 weeks between injections).
I don't know about larger doses, but occasionally a story pops-up about someone who hit the hard stuff way to long and did something permanent.