Young teenagers with extreme gender identity disorder should be given drugs to block puberty so that they don't have to experience distressing changes to their bodies which they perceive to be out of line with their true gender.
So say draft international guidelines issued by the Endocrine Society this week – the first to offer advice to doctors on this controversial issue.
The hope is that by delaying puberty, young teens will be given valuable thinking time in which they can decide if they are sure they want to begin gender reassignment using cross-sex hormones at the age of 16.
Ultimately, this strategy would also make it easier for them to live in their chosen gender. For example, potential male-to-female transsexuals will not have developed the deep voice, facial changes and body hair associated with adult masculinity. Gender-reassignment surgery should be avoided until the age of 18, the guidelines say.
"We recommend that adolescents who fulfill eligibility and readiness criteria for gender reassignment initially undergo treatment to suppress pubertal development," say the guidelines.
They state that treatment should not begin before Tanner stage 2 or 3: when female breasts have begun to bud, and boys have experienced a slight enlargement of the penis and scrotum. This is because the teenager's emotional reaction to these first physical changes can help predict whether they will persist in wanting to change their sex.
The recommendations are largely based on the experience of a clinic in the Netherlands where doctors have so far prescribed puberty blockers to more than 70 under-16s. The youngest they have treated is 11, although the majority are 12 or over.
"We don't have any patient who has regretted their decision on the treatment," says Henriette Delemarre-van de Waal of Leiden University Medical Centre who has helped treat them.
Clinics in other countries have also begun to offer the treatment, including Canada, Australia, Germany, and a handful of clinics in the US. However, it remains deeply controversial, with countries including the UK refusing to allow medical intervention until the age of 16, by which time puberty is usually in full swing.
At the heart of the issue is the fear that teenagers will change their minds. For example, previous studies have suggested that just 20% of boys who show signs of gender identity disorder in childhood continue to show it into adulthood.
And although the effects of puberty-blockers are reversible - natural puberty would resume if the teenager came off them – there have been few trials exploring the long-term effects of delaying puberty in this way.
"The real question is: if you intervene early in a young person who would otherwise change [their mind], do you reinforce their gender identity disorder? Do you remove the chance for change?" says Russell Viner of the Institute of Child Health in London.
There is also the issue of fertility. Blocking puberty in boys before mature sperm have had the chance to develop removes the option of freezing sperm in case they later decide they want to start a family after going ahead with gender-reassignment surgery.
"We recently had the case in the US of a transsexual man who chose to become pregnant, and that may not have been possible if they had had early intervention," says Viner. "When is it reasonable to let a young person remove major life choices?"