My son has been on Hormones since he was 11. He is biologically female. He was on puberty blockers from age 11 (given mainly because he had severe menorrhagia with 4 month cycles, 2 days break before they started again and no other medication worked). Since 18 he has been on Testosterone.
2 weeks ago he had top surgery age 20.
Both he and I were made well aware of what side effects of the hormones are and this is why you are constantly monitored while on them.
My son has lived as a boy since he was 4 years old. I thought it was just being a Tom Boy but his school eventually referred him to Tavistock when he was 7 and he was with them until transferred to Adult Services at 18. He has never ever changed his mind.
He has no LGBT friends, has not been brain washed and truly hates the sex he was born as.
As his mother I have just supported him all these years, not pushed him to transition and I have cried many tears over the years at loosing my daughter even though I gained a son.
My son does actually believe a lot of kids suddenly thinking they are trans is becoming a trendy fad. He believes if your trans then you would have known this all your life. He cant understand someone at age 16 for example suddenly believing they are transgender.
He said at his secondary school some kids with no friends would suddenly announce they were trans so they could join the group of kids who were and be accepted.
Despite all the rubbish in the news about Tavistock, they did not just dole out hormones, you spent years having counselling and it was actually hard to get any hormonal help and you had to jump through so many hoops.
If your teen is on hormones without being under a GIC then they are doing DIY which is very dangerous.
My son gets them via the NHS and has to have blood work done every 3 months to monitor the levels.
If your child believes they are trans then they need to go on the wait list for an NHS Gender Clinic where the current wait time is in years not months.