There are no chromosome problem. Teens are jumping into this new fad for a number of reasons. Girls, especially are on the rise. In the UK, children the percentage of children referred to gender clinics is up 1000% since 2009. It may be due to mental health issues, being on the Autistic Spectrum, result of being sexually assaulted, or not wanting to conform to what a woman is told she has to do. There is a social contagion going on through social network sites. Kids are getting coached by adult trans people on-line and are even taught that if their parents don't support them, then cut off ties. 

I know because my daughter is caught in this cult. It's a nightmare especially for the parents who don't buy into it. I'm scared to death to think that she could start hormones and have surgery anytime that she decides to now that she's 18. This could sterilize her for life. It took her a couple of months to get her name and sex designation officially changed without any doctor's signature.