This could also just be an issue you shouldn't worry about. I can only speak for myself here, but I think it's better to first take care of yourself. If you have real transgender feelings, then hormones should be the right choice for you, and not being able to produce offspring should only be a minor side-effect compared to the happiness you feel as a result of becoming / being yourself.
I know that this is a strong urge that most people born male feel. I felt them too. The urge to reproduce is natural and it's completely normal. It's always a comforting thought to think that your offspring will carry your genes. But at the end of the day, you have to think of the reality of the situation here; your genes are not that special in this world. Mine aren't either. I know I might sound like a complete downer saying this, but I think it's a harsh truth that not many people realize. There are seven billion people (!) on this planet, so the idea that your genes really add that much in the grand scheme of things is just a comforting fairy-tail in my opinion.
I think it is much more noble to educate and help the people that already here on the planet, instead of contributing to the increasing problem of overpopulation. But again this is just my opinion, and I hope it helps you cope with not being able to have biological children. In the end, it is you as an individual that matters.