I'm not sure why I'm bothering...but
@FrackOff
Blockers have been in use for years for other conditions, so would have gone through double blind trials before becoming available. Re blocker side effects, like any medication it's a question of how much someone feels they need it.
You really have no idea how the pharmaceutical industry develops, licenses and regulates drugs, do you? Or how paediatric clinical trials work?
Lupron (and other GnRH analogues) were originally FDA licensed to for use in end-stage prostate cancer. In 1993, the makers of Lupron applied for (and got) a license for use on children with precocious puberty. They have never been licensed for suppressing puberty in trans kids, and are therefore being used off-label. Where drugs are being used off-label, the manufacturer has no liability for adverse side-effects. It should be noted that off-label use results in a higher incidence of adverse drug events - journal article on adults here which refers to children
I'd like to point to you to the label and Abbvie's own clinical trials site which contains some interesting information on what studies were actually done:
label here
easy-to-read information on the Phase 3/4 trials here
If you actually look at the data, actual Phase 3 / 4 results here average treatment length was 4 years, with a follow-up 4 months after the final injection. No longer term safety studies were carried out prior to the license being granted.
The Phase 3 study indicated that adverse effects caused by treatment occurred in 62% of subjects, of which the most common were emotional lability, rash, acne and vasodilation, while 94.5% reported treatment-emergent adverse events. Severe adverse events were reported in 7 of the 55 children that took part in the Phase 3 study.
The longer-term safety studies (Phase 4) relate solely to final adult height and restoration of fertility. If you actually look at the secondary endpoints of the study, while they say "Girls resumed reproductive development following treatment with 1-month LUPRON DEPOT-PED1", this was based on a post-treatment survey of 20 girls, of whom 20% reported abnormal menstrual cycles. 10% of males showed no signs of Tanner stage advancement in the 6 months following cessation of treatment. Although bone density was included in the Phase 3 study, it was not included in the Phase 4 study, despite irreversible bone thinning noted as a complication in the adult label.
The label itself notes that no clinical trials have been performed to assess resumption of fertility: Although no clinical studies have been completed in children to assess the full reversibility of fertility suppression, but points instead to animal studies.
No long-term studies were performed on carcinogenesis or mutagenesis on children, instead they relied on animal studies and effects in adult patients (with a maximum treatment length of 2 to 3 years - dependent on dosage).
So no, puberty blockers have not gone through any double blind trials in the way that you seem to think, the long-term effect has not been studied (as the original indication was for end-stage prostate cancer, no long-term studies were required) and the safety data is extremely questionable.