We have evidence of harm caused by these drugs, and no clear evidence of benefit.
In the news today, there is discussion of expanding the use of chemical castration of sex offenders in prison, using drugs which are "widely used to treat prostate cancer". The news articles are a bit coy about specifying which drugs are used, which some doctors are apparently "uneasy" about using on sex offenders.
What is chemical castration? Here's why doctors will be uneasy about using it on sex offenders | UK News | Sky News
I had a quick look to see if I could find which drugs they were talking about, because I thought this could be the same drugs (GnRH agonists) as those which are commonly referred to as "puberty blockers", since these are often used in the treatment of prostate cancer.
I found this paper published last year.
Evaluation of selective-serotonin reuptake inhibitors and anti-androgens to manage sexual compulsivity in individuals serving a custodial sentence for a sexual offence
To address this gap in the appropriate treatment of PSA in the UK, HMPPS introduced medication as a treatment pathway to manage PSA. In 2007, they facilitated a pilot trial of this novel pathway (Medication to Manage Sexual Arousal; MMSA), which is ongoing. Currently, three types of medication are utilised within the UK prison estate: Anti-Androgens (AAs; Cyproterone Acetate [CPA]), Gonadotropin-Releasing Hormone Agonists (GnRH Agonists; Triptorelin) and Selective-Serotonin Reuptake Inhibitors (SSRIs; Fluoxetine/Paroxetine)
The GnRH Agonist Triptorelin is a "puberty blocker" which is used on trans-identifying children in the UK.
So doctors are "uneasy" about using this drug on sex offenders because of the potential side effects, but there are still those who think it could be ethical to conduct a trial using this drug on healthy children because those children believe that they are transsexual.