This is a tough one. It depends on a few things. One is how many changes you plan on making (I see HRT, are you growing your hair, getting ears pierced, etc), the duration you will be gone, and if your parents tend to notice details or are completely ambivalent. My mother never said a thing directly as I went through changes over about 7-8 years and she only saw me about three times. She made one comment about not wanting to see me not coming out of a room in a tutu which was at a minimum a tell that she noticed something was up. So if they are observant at all, they will notice as you are their child.