Hey Ivekan
I'm an old participant here, and tend to kill off my account until I find some reason to recreate it and respond to someone. How are you doing with your dilemma?
Some comments: firstly, you are extremely expressive and seem to be more than smart. This is a huge positive point in making a success of your life. But being smart can also lead to "analysis paralysis". I often suggest to people with a dilemma to create a table of all the concerns, and to write an honest response for the options and weigh them up. Your options, as I see them are "do nothing", "do something now", and "do something later".
Some of us manage to put our dysphoria into a box and work on other aspects of our lives. This could work for you if you are driven by your professional goals, for example. However (uh oh) I will echo what others have said, in that dysphoria may wax and wane, but tends to come back. I wanted to change over 25 years ago, but I was too scared and sublimated this desire into working hard, starting a few small companies and so on. But for many of us, our true selves simply need to be expressed sooner or later. I'm not saying that this is a ticking bomb, but I will say that life is so much better if you live it by being true to yourself in all aspects. I did this 5 years ago, and it worked out very well, partly because I planned it extremely carefully and knew exactly what I wanted to do.
Parents? The vast majority of them just want the best for their child, and most of them come round, even if they are shocked at first. They will question your motives because of your relative youth, and this is reasonable. But if you are prepared, and know your mind and have your story clear, they will almost certainly support you.
Do this now or later? Oh, this is the biggie! If you wait until you are successfully established in your professional (and personal) life, it is likely that you will successfully manage your transition and come out the other side equally successfully. There may be collateral damage, and you can't plan for everything (I got divorced and hurt someone I loved). If you do it now, you appear to feel that it would jeopardise your fututre, but I'm not so sure of this. You say you want to work in a medical environment, and this is possibly one of the best places to find people who are most sensitised to transgender issues. And, due to some recent high visibility transgender people, society in general is much more aware and less critical. To you I say grow a thick skin, and to your critics, tell them to jump.
My personal experience, to give you some context: I started transition when I was 45 and finished it a year later. That year was the most fascinating and positive one of my life, and my friends, family and company were fully supportive. Because people now see someone credible and positive, most of them can't remember how I was before. My key regret is not having done this 20 years earlier, but these are moments, and I get on with living in the here and now.
I wish you the best of luck, but let me tell you that you almost always make your own luck, and that is what you should do!
Julia