A significant number of people who identity as trans later return to their original gender identity. This is known as "detransitioning:"
https://www.thestranger.com/features/2017/06/28/25252342/the...
It's a controversial topic, as many trans people see the existence of detrans people as a threat to the validity of their own identity. For their part, many detrans people resent the medical practitioners who they feel didn't adequately provide council or obtain informed consent before facilitating their transition, sometimes involving expensive, painful, and irreversible medical procedures. Some research also indicates most (!) children who identify as trans abandon this identity post-puberty:
https://www.kqed.org/futureofyou/441784/the-controversial-re...
The Blocked and Reported podcast, which I generally find to be fair-minded and evenhanded, recently interviewed a detrans person who had worked at a SF gender transition clinic. I found their experience illuminating:
https://barpodcast.fireside.fm/50
The BBC and 60 Minutes have also produced reporting on this issue.