If puberty starts at 7, bad stuff happens. Delaying it for 5 years in girls, 7 in boys, is recommended in such cases.
Using the same medications on Transsexual children in controversial still. The evidence is clear that it saves lives if you do, in the short term. There's been no evidence of harm in the 22 years since this was first started overseas, but the numbers are too small to be certain there's no long-term ill effects.
In Holland, they wait till at least age 12. In the US, until Tanner stage II, which may come earlier, or later - 15 or so in some cases. Only about 100 transsexual children have been so treated in the USA, none in California to my knowledge.