First of all, never look to the Heritage Foundation for medical information of any kind. That is not what they do. They exist as a means of enshrining a particular brand of conservative Protestant Christianity into United States law. You can love 'em, you can hate 'em, you can not care about 'em, but never confuse them with doctors, psychologists, or academic researchers.
For those who may be uncertain of how medical transition works, both for adults and minors, I will describe it briefly.
Prepubescent children: Kids who have not yet reached puberty aren't usually described as "trans" at all. The preferred term is "gender expansive," which is a way to acknowledge that a kid isn't interested in staying in their little assigned gender box, without saying for certain what their adult gender identity is going to be. Younger kids don't "medically transition" as such, because there's not really a need to. If a kid is 6, just let them have a hairstyle and clothes that make them comfortable. Roll with name and pronoun preferences, which may well change. No, you do not have to alter records at the kid's elementary school and pediatrician every other day, because a small kid doesn't know about that stuff and doesn't care.
Pubescent children: If a kid is showing signs of entering puberty and the changes are distressing them, you can essentially "hit the pause button" with puberty blockers. Personally, I'd like to see this option given to cis children as well. Early-developing girls in particular frequently find themselves in sexually-charged situations that they don't entirely understand and do not feel ready for. This can happen to any child, however, whatever their gender or sexual orientation. Puberty blockers can safely be used for quite a long time. I do know one person who took them into early adulthood. That was an unusual situation, but even so, there were no ill effects. That young person decided which direction they wanted their puberty to go during their first or second year as a college student, and they're fine.
Older adolescents: Young people mature at different rates, so I can't give a "magic age" at which all of them are able to make mature and informed decisions for themselves. However, I think anyone who has been a caregiver for kids approaching adulthood understands that there is a transitional period of time where young people's desires and preferences are given significant weight, but guardian adults make the final decision. A framework for this situation already exists for trans kids, in the form of WPATH guidelines. These have actually just been updated with specific regard to minors. For the record, I think WPATH is damn weird when applied to fully grown adults, which it often is. I medically transitioned in my mid-40's. I still had to play "Mother May I" and get written permission from my therapist in order to start hormones and seek surgery. While that's inappropriate for a middle-aged person, I think it can make sense when the patient seeking medical transition is in the gray zone between 15 and 17.
Not that anyone asked, but:
1) Please be aware that HRT is not birth control. Unless a surgeon has actually gone in and disconnected your babymakin' bits, you can be, or can get someone else, pregnant. Proceed with due caution.
2) It's EXTREMELY difficult to get surgically sterilized if you are a person who owns a womb. Nobody is giving elective hysterectomies to minors. I'm having a hell of a time getting one, and I'm nearly 50. Nobody's giving vasectomies to minors, either, although if you're 18+ and AMAB you're allowed more autonomy over your body.
www.washingtonexaminer.com
,is that terrible crimes are being committed against young people. 
