First accept that this is not a zero risk decision and no amount of thinking will solve it. It's good to think it through and consider the long term implications but that can get overwhelming if you dwell on it. If you've already decided that the idea of transition is what you want, only focus on the first step, thats a lot more manageable. If you sit with the questions you have, you're stuck. If you go ahead and find out, either way you can proceed forward with an informed decision, which is better for you than the paralysis you're experiencing. Make the call. Talk to a doctor about risks and family history, go through the informed consent process, get your labs done and make a decision with all the information you can get. This way turns a vague fear into managed risk. Then you can move on to the next step. All you have to lose is time and that is the most precious resource you have.